Microscopy etching techniques

Riehie U and Hdchii M 1973 The theory and technique of high pressure freezing Freeze-Etching Technique and Appiications ed E L Benedetti and P Favard (Paris Societe Frangaise de Microscopie Eiectronique) pp 31-61... 

A progressive etching technique (39,40), combined with x-ray diffraction analysis, revealed the presence of a number of a polytypes within a single crystal of sihcon carbide. Work using lattice imaging techniques via transmission electron microscopy has shown that a-siUcon carbide formed by transformation from the P-phase (cubic) can consist of a number of the a polytypes in a syntactic array (41). 

J. H. M. Willison and A. J. Rowe, Replica, Shadowing and Freeze-etching Techniques , in Practical Methods in Electron Microscopy, Vol. 8 (ed. A. M. Glauert), North-Holland, Amsterdam, 1980, pp. 31-55. 

The presence of liquid-crystalline material at the emulsion interface has been shown by electron microscopy using the freeze-etching technique 18). Typical liquid-crystalline structures are shown in Figure 16. These liquid-crystalline compositions are viscous, and the lamellar phase displays pseudoplastic rheology. The lamellar phase is the most important of all liquid-crystalline phases for emulsion stability. The presence of a liquid-crystalline phase causes a reduction of the available London-van der Waals forces for coalescence 16). As a consequence of the reduction of the influence of these dispersion forces and the high viscosity of the liquid-crystal layer, the time for coalescence is increased dramatically. 

Freeze-etching Technique in which water is evaporated under vacuum from the freeze-fractured surface of a specimen before the observation with electron microscopy. 

There is also a finer texture of scale less than 100 nm, which may correspond to segregation of the two different chemical parts, namely the HS and SS. This is only observed by operating the SEM at higher accelerating voltage and smaller spot size, as in Fig. 2.22 f. Shown here is PUm pthf. but finer structure is present in the other materials also. This, however, was not intensively studied, as it would require transmission electron microscopy to give appropriate resolution, and such examination would be better if a suitable chemical etching technique were available to reveal the bulk of the material and remove features associated with the surface. 

Different specimen types yield a range of results upon ion or plasma etching. Multiphase polymers generally etch differentially, enhancing the contrast. Melt crystallized polymers can be etched to reveal the spherulites. Surface protuberances and particulate fillers can and do form cones or ridges when etched. Oriented semicrystalline polymers, on the other hand, appear to be the most controversial with respect to the resulting surface textures. Clearly, in such cases the specimen should be prepared by other methods for comparison, and control experiments are essential. There are problems in the industrial laboratory that can be solved, in part, by microscopy of surfaces prepared by etching techniques however, these are far fewer than those addressed by other specimen preparation methods. 

The most powerful method for the identification of the different phases and for the determination of their microstmctures is the transmission electron microscopy. This method requires a sample preparation using the freeze fracture and etching technique. With these measurements the microstructures of the various phases can be visualized directly. This is shown for three examples in Fig. 11.12 (Section 11.4.2) and in Figs. 11.30a and 11.30b [13,41, 97]. 

Benedetti, E.L., and Favaerd, R, Freeze Etching Techniques and Applications, Soci6t6 Franpaise de Microscopie Electronique, 1973. 

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