New generation scanning electron microscopy technology based on the concept of active image processing

A new generation of scanning electron microscopy (SEM) technology is proposed based on the concept of “active image processing.” In order to collect sufficient data for a purpose which is defined in the utilization of active image processing, we may need more devices from among a variety of useful hardware, for example, a digital scan generator with meaningful parameters and an analog-to-digital converter for ultrahigh density recording. After the data acquisition, the application of some digital image processing techniques is certainly effective, because the method in question is specially designed so that the property of obtained data will be suitable for the application of these techniques. The present technology should produce a variety of attractive options in the field of SEM.     

Stress corrosion cracking countermeasure observed on Ni-based alloy welds of BWR core support structure

The effect of hydrostatic test on the residual stress re-distribution was simulated by experiment to confirm the residual stress behavior of the cone-shaped shroud support to reactor pressure vessel (RPV) weld, where a number of cracks due to stress corrosion cracking (SCC) were observed on the inner side only. Test specimen with tensile residual stress was loaded and unloaded with axial plus bending load, which simulates the hydrostatic test load, and the strain change was measured during the test to observe the residual stress behavior. The results verify that the residual stresses of the shroud support to the RPV weld were reduced and the stresses on inner and outer sides were reversed by the hydrostatic test. As the SCC countermeasure, the shot peening (SP) technology was applied. Residual stress reduction by SP on the complicated configuration, and improvement of SCC resistance and endurance of the compressive residual stress were experimentally confirmed. Then, SP treatment procedures on the actual structure were confirmed and a field application technique was established.     

Assessment of low-cycle fatigue life of Sn-3.5mass%Ag-X (X=Bi or Cu) alloy by strain range partitioning approach

The fatigue lives and damage mechanisms of Sn-Ag-X (X=Bi and Cu) solder alloys under creep-fatigue interaction mode have been investigated, and the adaptability of the strain partitioning approach to the creep-fatigue of these alloys was examined. Symmetrical and asymmetrical saw-tooth strain profiles components (i.e., fast-fast, fast-slow, slow-fast and slow-slow) were employed. Application of the slow slow,strain mode did not have an effect on fatigue lives of the alloys under investigation. Transgranular fracture observed on the fracture surfaces suggests that creep damage might be cancelled under slowslow mode. The fatigue lives of all alloys were dramatically reduced under slowfast mode, which is attributed to intergranular cavitation and fracture during tensile creep flow. On the other hand, the compression creep component generated by fast-slow mode also significantly reduced the life of Sn-3.5Ag and Sn-3.5Ag-1Cu, while the component did not affect the life of Sn-3.5Ag-xBi (x=2 and 5). The four partitioned strain ranges (i.e.,_{p, pp, cp}, and _cc) versus life relationships were established in all alloys tested. Thus, it is confirmed that the creep-fatigue life of these alloys can be quantitatively predicted by the strain partitioning approach for any type of inelastic strain cycling.     

A new non-linear pseudo-Laplacian filter for enhancement of secondary electron images

A simple, yet effective, non-linear pseudo-Laplacian filter has been newly developed to enhance secondary electron (SE) images. This filter is a combination of the second derivative along the direction of the local gradient and a non-linear weight factor. The filter can successfully enhance SE images without the undesirable effects of noise which are often seen in conventional Laplacian filtered images. Hence, the processed results with high image quality can make original SE images easier to interpret. The effectiveness is especially useful in low-voltage scanning electron microscopy, because SE images taken at low voltages are not so likely to have good image sharpness.     

New versatile staining reagents for biological transmission electron microscopy that substitute for uranyl acetate

Aqueous uranyl acetate has been extensively used as a superb staining reagent for transmission electron microscopy of biological materials. However, recent regulation of nuclear fuel material severely restricts its use even for purely scientific purposes. Since uranyl salts are hazardous due to biological toxicity and remaining radioactivity, development of safe and non-radioactive substitutes is greatly anticipated. We examined two lanthanide salts, samarium triacetate and gadolinium triacetate, and found that 1-10% solution of these reagents was safe but still possess excellent capability for staining thin sections of plastic-embedded materials of animal and plant origin. Although post-fixation with osmium tetroxide was essential for high-contrast staining, post-staining with lead citrate could be eliminated if a slow-scan CCD camera is available for observation. These lanthanide salts can also be utilized as good negative-staining reagents to study supramolecular architecture of biological macromolecules. They were not as effective as a fixative of protein assembly, reflecting the non-hazardous nature of the reagents.