Deformation feature, electron microscopy

Carr and his co-workers [86C01, 87C01] have shown that transmission electron microscopy is a powerful tool in characterizing linear and higher-order defect configurations and their densities on shock-modified rutile, alumina, aluminum nitride, and zirconia [84H02]. The principal impediment to detailed characterization of shock-formed defects is their very high concentrations, which prevent identification of specific deformation features except in... 

A transmission electron micrograph of a craze in a thin film of poly(styrene-acrylo-nitrile), shown in Fig. 1 a, will serve to introduce the principal microstructural features of crazes. The direction of the tensile stress is marked and it can be seen that the craze grows with the primary direction of its fibrils parallel to this tensUe stress and with the interfaces between the craze and the nearly undeformed polymer matrix normal to the stress. Since the overwhelming portion of the experiments to be reviewed here rely on the use of thin film deformation and transmission electron microscopy techniques, a brief review of the general methods of these experiments is in order. 

Deformed quartz samples obtained from shock-recovery experiments were generally investigated with TEM (transmission electron microscopy) to study their planar deformation features. Furthermore, several studies on the atomic-scale structure of diaplectic quartz glass have been carried out by using X-ray diffraction and IR (infrared) and Raman spectroscopy techniques. In the next section, some recent structural investigations of diaplectic quartz glass will be reviewed. 

These features suggest the following picture for the deformation of this type of steel at very low temperature the stress produces a deformation due to the motion of dislocations (effect visible by electron microscopy). These motions induce a transitory phase e in the lattice, and this e phase rapidly evolves toward the a phase. The martensitic a phase is therefore only a secondary phenomenon bound to the dislocation motion and a simple function of the strain associated with this motion. 

In order to supplement micro-mechanical investigations and advance knowledge of the fracture process, micro-mechanical measurements in the deformation zone are required to determine local stresses and strains. In RTFs craze zones can develop that are important microscopic features around a crack tip governing strength behavior. Plastics fracture is preceded by the formation of a craze zone that is a wedge shaped region spanned by oriented micro-fibrils. Methods of craze zone measurements include optical emission spectroscopy, diffraction techniques, scanning electron microscope, and transmission electron microscopy. 

Other artifacts that have been mentioned arise from the sensitivity of STM to local electronic structure, and the sensitivity of SFM to the rigidity of the sample s surface. Regions of variable conductivity will be convolved with topographic features in STM, and soft surfaces can deform under the pressure of the SFM tip. The latter can be addressed by operating SFM in the attractive mode, at some sacrifice in the lateral resolution. A limitation of both techniques is their inability to distinguish among atomic species, except in a limited number of circumstances with STM microscopy. 

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