REPLICA AND SHADOWING TECHNIQUES 



5in g lB 5to q e Method 

 Pop Particles 



Por+icles 



Double Sto p e Method 

 Por Surfoce 5tructure 



\q-Ioss slide 



(0 



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0) 



-^^^S><!S^^S- 



(I D 



Corbon 



P\OS\\Q. 



(11) 



S6lVENT Fi^RC^ 

 PARTICLES 



Ciii) 



Carbon^ 

 Loyen 



/=iLJj=^^^^^7L^ 



Plastic 



O'O 



Pinal Replica 



C'v) 



Pinal Replica 



Fig. 3. Diagrammatic representation of two basic carbon replica methods. (By courtesy of the 

 Journal of Applied Physics) 



is ground, polished and etched, so as to 

 leave the precipitates protruding above the 

 matrix. The surface is then coated with a 

 thin film of carbon and subsequently more 

 of the matrix is dissolved by continued etch- 

 ing through the carbon film. This has the 

 effect of releasing many secondary phase 

 inclusions, and when the carbon replica is 

 removed from the metal surface, either by 

 electro-polishing or floating onto water, the 

 secondary-phase inclusions remain attached 



to it. The film can now be mounted on an 

 electron microscope grid. 



The precipitates are sometimes too thick 

 to permit identification by electron diffrac- 

 tion. However, Booker has identified such 

 crystals by rolling the replica up and insert- 

 ing it into an X-ray diffraction camera. 

 Figure 5 shows a typical extraction replica; 

 this contains two secondary phases, fine 

 needles (M02C) and larger particles (CtiCz). 



233 



