Materials Problems and Approaches for TEM and TEM/STEM Analyses - Sample Preparation Topic for Transmission Electron Microscopy - page 66

The structural investigation of polymer materials focuses on multiphase poly-
mers and makes it possible to determine the different phases and their coherence.
For semi-crystalline polymers, highly localized crystallographic investigations can
be planned.
The structure of stabilized bulk biological materials, prepared by ultramicro-
tomy, is essentially observed in bright-field imaging mode. In certain cases, it can
be observed under energy-filtered imaging mode or in annular dark-field mode.
The information given in the image must be conceptualized in terms of volume,
because a TEM image is a projected 2D image of a sample. The image is of a plane
in which all the elements present in the thickness of the section are found superim-
posed and merged. TEM analysis of structural components as collagen fibers require
specimen orientation to image the fibers (Fig. 4.5) .

a b

c

2

1

Fig. 4.5 TEM images of collagen fibers: ( a ) cross section and ( b ) longitudinal section. In the latter,
we can see the transverse lines of the fiber, which have a periodicity of 65 nm. We may note at the
bottom right-hand side in ( a ), collagen fibers viewed from an ordinary longitudinal-plane section
do not allow us to determine their diameter and their periodicity. In ( c ), the diagram represents two
types of sections in TEM images: (1) longitudinal and (2) cross section ( J. Boumendil CMEABG,
Université Claude Bernard-Lyon 1 Villeurbanne )

In the example shown in Fig. 4.6, a retrovirus can be confirmed as coming out
of the cell only if it can be seen budding (arrow in Fig. 4.6a ). In the other cases, a
conclusion cannot be reached. As Fig. 4.6b shows, superimposing the various planes