Local Lattice Deformation of Tellurene Grain Boundaries by Four-Dimensional Electron Microscopy

It is possible to produce metallic materials with submicrometer-grained (SMG) structures by imposing an intense plastic strain under quasi-hydrostatic pressure. Studies using conventional transmission electron microscopy (CTEM) showed that many grain boundaries in the SMG structures appeared diffuse in nature with poorly defined transition zones between individual grains. The implication of the CTEM observations is that the grain boundaries of the SMG structures are in a high energy state, having non-equilibrium character. It is anticipated that high-resolution electron microscopy (HREM) will serve to reveal a precise nature of the grain boundary structure in SMG materials. A recent study on nanocrystalline Ni and Ni3Al showed lattice distortion and dilatations in the vicinity of the grain boundaries. In this study, HREM observations are undertaken to examine the atomic structure of grain boundaries in an SMG Al-based Al-Mg alloy.An Al-3%Mg solid solution alloy was subjected to torsion straining to produce an equiaxed grain structure with an average grain size of ~0.09 μm.

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Surface reconstructions of (001) cleaved GdBa2Cu3O7-δ

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010012093x ◽

1992 ◽

Vol 50 (1) ◽

pp. 106-107

Author(s):

H.W. Zandbergen ◽

M.R. McCartney

Keyword(s):

Electron Microscopy ◽

Copper Oxide ◽

Grain Boundaries ◽

Atomic Structure ◽

Oxygen Deficiency ◽

Surface Layers ◽

Layer Sequence ◽

Surface Reconstructions ◽

Good Agreement

Very few electron microscopy papers have been published on the atomic structure of the copper oxide based superconductor surfaces. Zandbergen et al. have reported that the surface of YBa2Cu3O7-δ was such that the terminating layer sequence is bulk-Y-CuO2-BaO-CuO-BaO, whereas the interruption at the grain boundaries is bulk-Y-CuO2-BaO-CuO. Bursill et al. reported that HREM images of the termination at the surface are in good agreement with calculated images with the same layer sequence as observed by Zandbergen et al. but with some oxygen deficiency in the two surface layers. In both studies only one or a few surfaces were studied.

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High-resolution electron microscopy of nanostructured materials

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100137239 ◽

1995 ◽

Vol 53 ◽

pp. 172-173

Author(s):

M. José-Yacamán

Keyword(s):

Electron Microscopy ◽

High Resolution ◽

Grain Boundaries ◽

Nanostructured Materials ◽

High Resolution Electron Microscopy ◽

Hrem Image ◽

Small Particles ◽

Resolution Electron ◽

Nanophase Materials

Electron microscopy is a fundamental tool in materials characterization. In the case of nanostructured materials we are looking for features with a size in the nanometer range. Therefore often the conventional TEM techniques are not enough for characterization of nanophases. High Resolution Electron Microscopy (HREM), is a key technique in order to characterize those materials with a resolution of ~ 1.7A. High resolution studies of metallic nanostructured materials has been also reported in the literature. It is concluded that boundaries in nanophase materials are similar in structure to the regular grain boundaries. That work therefore did not confirm the early hipothesis on the field that grain boundaries in nanostructured materials have a special behavior. We will show in this paper that by a combination of HREM image processing, and image calculations, it is possible to prove that small particles and coalesced grains have a significant surface roughness, as well as large internal strain.

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