Double hexagonal superstructure of Au–Mg alloy containing 20 at.% Mg studied by high-voltage high-resolution electron microscopy

1983 ◽  
Vol 16 (2) ◽  
pp. 233-238 ◽  
Author(s):  
D. Shindo ◽  
K. Haraga ◽  
M. Hirabayashi ◽  
O. Terasaki ◽  
D. Watanabe

High-resolution observations of Au–20.2 at.% Mg alloy have been carried out by using a 1 MV electron microscope. The many-beam images with the [001] axial illumination are interpreted in terms of the double hexagonal superstructure of 9a 0−4H type. With the aid of computer simulations by the multislice method, it is revealed that two kinds of interpretable image are obtained for different specimen thicknesses at the optimum defocus. The imaging conditions are discussed in comparison with the orthorhombic structure of the D023 type.

1987 ◽  
Vol 111 ◽  
Author(s):  
D. R. Acosta ◽  
O. Guzman ◽  
P. Del Angel ◽  
J. Dominguez

High resolution electron microscopy has proven to be a powerful technique to determine structural characteristics of zeolites (l–2),symmetry variations and identification of several kind of defects.Together with ideal projected potential images, the microscopist usually finds in electron micrographs the influence of electro-optical parameters and alterations of the crystallinity of the material under electron irradiation. One of the purposes of this workis to contributetothe understanding of the degradation process of zeolites under electron irradiation in the electron microscope and in this way, discriminate when it is possible, what is reliable information recorded in the images obtained in high resolution conditions.


Author(s):  
R. Csencsits

High resolution electron microscopy (HREM) is a valuable technique for studying catalytic zeolite systems because it gives direct information about the structure and defects present in the structure. The difficulty with doing an HREM study on zeolites is that they become amorphous under electron irradiation. This work is a systematic investigation of the damage of Y zeolites in the transmission electron microscope (TEM); the goals of this study are to determine the mechanism for electron damage and to access the effects of damage in Y zeolites on their HREM images using computer simulation.


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