Field emission scanning electron microscope has evolved in which the electron beam cross section has become smaller and smaller increasing magnification several fold. Raw red mud and modified red mud were characterized by Field Emission Scanning Electron Microscopy (FESEM), as shown in Figure25. The FESEM analysis showed that the raw red mud consisted of aggregates, including particles of different dimensions. The FESEM image of the PRM and ORM showed a very fine distribution of particles with a size of 64 and 71 nm respectively as shown in Fig. 7. While ORM showed a homogenous distribution of particles than raw red mud with particle size larger than PRM due to formation of organic coating around the particles.
Fig. 25. FESEM images depicting size of a single red mud particle (a) Phosphomolybdic acid modified red mud (PRM), (b) Organically modified red mud (ORM)