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Publisher Summary This chapter reviews the current results about high-resolution electron microscopy studies on quasicrystals. From the results it can be concluded that structures of icosahedral and decagonal quasicrystals can be described as aperiodic arrangements of some atom clusters, which have the same symmetry as those of the quasicrystals, with definite linkages. There is variety in aperiodic arrangement of the atom clusters and atomic arrangements in the atom clusters, depending on quasicrystalline alloys. High-resolution electron microscopy is the most powerful tool for studying the varied structures. However, it has many limitations for carrying out precise structure analysis about atomic arrangements, because of its limited resolution compared with diffraction and the use of images projected along the incident beam. To proceed to the more precise structure analysis of the quasicrystals, combining high-resolution electron microscopy with the diffraction method becomes more important. The atomic arrangements of Al–Ni–Co, Al–Pd–Mn, and Al–Pd decagonal quasicrystals, were proposed using the results of x-ray diffraction.

Twins in the B19′ TiNi martensite have been investigated by conventional transmission electron microscopy (CTEM) and high resolution electron microscopy (HREM). Type II, {111} Type I, {011} Type I, (100) compound and (001) compound twins were reconfirmed. Lattice images of the Type I and the compound twins exhibit the well-defined crystallographic features of those boundaries. Lattice image of the Type II twin taken from the unique axis suggests that neither ledge nor step structures are present at the irrational boundary. Morphological aspects of the twins are also described.

The martensitic transformations in Ni50AlxMn50-x (16.0 ≤ x ≤ 20.5) alloys were extensively studied by DSC and electron microscopy. As a result, two new martensites with long period stacking order structures were found. They were identified by electron diffraction and high resolution electron microscopy to be 15R (32)3 martensite, and the mixture of 15R martensite and 7R martensite, respectively.

The structure of ETS-10 was studied by electron microscopy, combining high resolution electron microscopy(HREM), electron diffraction(ED) and scanning electron microscopy(SEM). Strong diffuse scattering is observed in the ED patterns due to extensive faulting and the nature of these faults and a manner of the arrangement are revealed by HREM. The basic structural unit is a rod consisting of tetrahedral SiO 4 and octahedral TiO 6 . From this unit we can describe the structures of a family of polymorphs, many of which are observed locally by HREM. One end member polymorph is a chiral and possesses a spiral channel . ETS-10 has three dimensional 12-ring pore system containing straight pores and pores which are twisted due to the faulting.

High resolution electron microscopy is a powerful tool in materials research. A number of questions concerning the synthesis and the properties of zeolites and the way in which electron microscopy might help to resolve them are discussed. Examples of several electron microscopy studies (nucleation of ZSM-5, defects in several zeolites, growth of denser phases on Zeolite L and Y, morphology changes of Zeolite L, metal particles in ZSM-5) are given.