Transmission electron microscopy boundary phase

The most significant advantage of these more quantitative methods is that, in a binary system, only one sample is needed to determine the position of both phase boimdaries in a two-phase field. Further, if the alloy lies in the two-phase field over a wide range of temperatures, it is feasible that only one alloy need be used to fix the phase boundaries over this range of temperature. In a ternary system the analogous position is found with three-phase fields and, as these also define the limiting tie-lines of the three sets of two-phase fields, substantial information can be gained from the accurate determination of only one alloy. More recently transmission electron microscopy (TEM) has been used which is particularly valuable when microstructures are very fine as, for example, found in yTiAl alloys (Chen et al. 1994). 

In this overview, we will first discuss how transmission electron microscopy (TEM) techniques can be used to determine the presence or absence of intergranular amorphous phases at interphase boundaries in structural... 

There is furthermore recent evidence from transmission electron microscopy (TEM) studies for the dissolution of matrix grains in the grain-boundary phase during oxidation at high temperatures, which widens the grain boundary films as a function of depth into the material [157,158]. This type of penetration will be even more difficult to detect and quantify. 

Figure 2.11. Morphology via transmission electron microscopy of the blend PVC/PBD (see Figure 2.8). Sharply defined phase boundaries indicate gross incompatibility.

High-powered microscopes can be used to reveal the internal structure, e.g. an interpenetrating phase, which is impossible to see with the naked eye. The normal technique used to observe phase boundaries under normal light is optical microscopy. However, as some blends have very tiny components, other more powerful techniques are required, i.e. transmission electron microscopy, scanning electron microscopy and atomic force microscopy. It should be noted that in order to see the structures clearly, preliminary treatments are sometimes necessary, for example etching or staining." ... 

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