Ultramicrotomy

Ultramicrotomy was one of the oldest sample preparation techniques used for soft biological specimens. With the improvement in instrumentation capabilities, this approach is making a comeback into the mainstream engineering materials, especially polymers. It involves directly sectioning an extremely thin sample using an ultramicrotome and dropping it in a liquid, where it will float and can latter be retrieved. A schematic of the ultra- 

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Specimens for (S)TEM have to be transparent to the electron beam. In order to get good contrast and resolution, they have to be thin enough to minimize inelastic scattering. The required thin sections of organic materials can be obtained by ultramicrotomy eitlier after embedding into suitable resms (mostly epoxy- or methacrylate resins [H]) or directly at low temperatures by cryo-ultramicrotomy [12]. 

Ultramicrotomy is sometimes also used to produce thin samples of solid materials, such as metals [13] which are, however, preferentially prepared by chemical- or ion-etching (see [1]) and focused ion beam (FIB) teclmiques [14]. 

FIGURE 20.4 (a, b) Height and phase images of rubber blend of natural rubber (NR) and butylene rubber (BR) (50 50), which were taken immediately after cryo-ultramicrotomy. (c, d) Height and phase images of the same sample location as in (a, b) taken 12 h later. 

Fig. 15 Super-lattices of iron nanocubes a SEM micrograph of a super-cube b TEM micrograph of a super lattice c TEM micrograph after ultramicrotomy...

High Resolution Transmission Electron Microscopy (HRTEM, Philips CM20, 200 kV) was applied to get structural and nanotextural information on the fibers, by imaging the profile of the aromatic carbon layers in the 002-lattice fringe mode. A carbon fiber coated with pyrolytic carbon was incorporated in epoxy resin and a transverse section obtained by ultramicrotomy was deposited on a holey carbon film. An in-house made image analysis procedure was used to get quantitative data on the composite. 

The identification of blood is generally performed using immunological tests. However, ToF-SIMS can also be used, with a different approach [Mazel et al. 2007]. Different objects, Dogon and Bamana, presenting thick patina were studied to prove whether or not blood was employed for making the patina. For each object, a microsample of patina was removed from the surface, and cross-sections were prepared by ultramicrotomy. 

Fig. 2. Composite figure illustrating (A) block trimming to atrapezoid, (B) TEM grids, (C) ultramicrotomy, and (D) section pickup. (B) and (C) from Watt (54) with permission. 

Prepare 1 -pm thick sections by ultramicrotomy (thin sections from ultramicrotomy of same blocks used for obtaining thick sections can be employed for EM radioautography). 

Fumeaux, R. C., G. E. Thompson and G. C. Wood. 1978. The application of ultramicrotomy to the electronoptical examination of surface films on aluminum. Corrosion Science 18 853-81. 

Pease, D. C. and Porter, K. R. 1981. Electron microscopy and ultramicrotomy. J. Cell Biol 91, 287s-292s. 

Ultramicrotomy Large thin areas that may not require additional thinning High amount of deformation not suitable for hard materials slow often irreproducible needs practice... 

As-synthesized, calcined and steam-treated samples of FeZSM-5 grown from stirred and unstirred gels with Si02/Fe203-ratios 2 50, 90 and 200 were studied. The specimens consisted of uniformly thin (50-80 nm) sections of the iron silicate particles embedded in an acrylic resin and were prepared by ultramicrotomy, described in detail elsewhere (13, 14). 

The FIB/lift-out technique yields cross sections of both the film and substrate, which maintains the integrity of the interface in comparison, ultramicrotomy requires the removal of the polymer film and subsequent embedding/sectioning. For a detailed example, see White, H. Pu, Y Rafailovich, M. Sokolov, J. King, A. H. Giannuzzi, L. A. Urbanik-Shannon, C. Kempshall, B. W. Eisenberg,... 

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