Specimen supports

Shape and form of the specimen support should assure free contact of the specimen with the corroding solution, the liquid line, or the vapor phase, as shown in Fig. 25-5. If clad alloys are ejq)osed, special procedures are required to ensure that only the cladding is ejq)osed (unless the purpose is to test the ability of the cladding to protect cut edges in the test solution). Some common supports are glass or... 

From a comparison of various spot electron diffraction patterns of a given crystal, a three-dimensional system of axis in the reeiproeal lattice may be established. The reeiproeal unit cell may be eompletely determined, if all the photographs indexed. For this it is sufficient to have two electron diffraction patterns and to know the angle between the seetions of the reeiproeal lattice represented by them, or to have three patterns which do not all have a particular row of points in common (Fig.5). Crystals of any compound usually grow with a particular face parallel to the surface of the specimen support. Various sections of the reciprocal lattice may, in this case, be obtained by the rotation method (Fig.5). 

The reciprocal lattice of single crystal is a system of points. In the case of a plate texture, the axis of the reciprocal lattice is perpendicular to the specimen support. When a plate texture specimen is perpendicular to the electron beam, the diffraction pattern becomes a system of concentric rings (equivalent to the rotation of single crystal about the texture axis). 

IZOD impact test—method for determining the behavior of materials subjected to shock loading. Specimen supported as a cantilever beam is strack by a weight at the end of a pendulum. Impact strength is determined from the amount of energy required to fracture the specimen. The specimen may be notched or unnotched. 

The brominated sticks are embedded in Spurr epoxy resin (Spurr 1969) and sectioned with a diamond knife or glass knife mounted on an ultramicrotome to give cross sections of 0.15//m thickness for TEM-EDXA or 0.5//m thickness for SEM-EDXA. The sections are then placed on a carbon-coated collodion film on the specimen support grid. The specimens are carbon-coated again to avoid charging. 

Since most materials are opaque to the electron beam, even when only a few hundred nanometers thick, special problems arise in the production of suitable mounted specimens. Specimen support films are usually made of plastic or carbon, though other materials have also been used. Suitable film solutions may be made up of 2% w/v formvar (polyvinyl formal) in ethylene dichloride or chloroform. 

W. Baumeisterand M. Hahn, Specimen supports, in Principles and Techniques of Electron Microscopy Biological Applications (ed. M. A. Hayat), Van Nostrand Reinhold, New York. 1978. 

The adherence of small particles of precious metals to the surface of the support can be assessed by transmission electron microscopy. It has been observed that mild ultrasonic treatment of the catalyst in a liquid, such as ethanol, can remove precious metal particles from the surface of the support. After applying a drop of the suspension resulting from the ultrasonic treatment on the carbon films used as specimen support the precious metal particles released from the support show up on the carbon support film. Especially dark-field techniques are useful to indicate the presence of precious metal particles on the carbon support film. 

Figure 20 Plan view of three meter cube smoke test (lEC 1034 I and 1034 2), I. Specimen supports. 2. Alcohol tray. 3. Draught screen. 4. Mixing fan. 5. Photo cell lamp system. 6. Entry door.

Figure 2. Two types of target specimen support used in FOD testing (a) fully supported and (b) partially supported (L=20 mm).

Backside damages in the target specimens were sensitive to the type of specimens support. At lower impact velocities <220 m/s, the backside damage appeared to be in stinguishable between the two supports. However, a remarkable difference in backside damage started at impact velocity >300 m/s No damage was observable in full support whereas. 

Figure 4. Summary of front impact damage with respect to impact velocity in oxide/oxide composite impacted by 1.59-mm steel ball projectiles in two types of full and partial specimen supports. Arrows indicate impact sites.

The bending beam rheometer (Figure 4.21) is composed of a loading frame with test specimen supports, a controlled low/very low temperature liquid bath that maintains the test specimen at the test temperature and provides a buoyant force to counterbalance the force resulting from the mass of the test specimen and a computer-controlled data acquisition system for the execution of the test and the processing of the results. 

In EDS the production of extraneous radiation is a problem, especially in TEM. During the irradiation of the specimen, electrons are scattered, and both characteristic and continuum X-rays are produced from materials in the surrounding area, such as the grid, the specimen support, and the lens pole pieces. Such extraneous contributions may cause errors by masking elements present in the specimen and by production of excess continuum, which causes problems in quantification. 

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