Artifacts etching

In any manner, even though some of the classical corrosion forms can be also found in archaeological finds, fhey are frequently configured in a very complex form—either from a morphological, structural, or chemical viewpoint. Moreover, corrosion products bear a large piece of information about the artifact s life and should not be inadvertently removed, contrarily to modern metals, which would simply be etched. It is a big challenge to conserve such objects. On the one hand, it... 

Normally the craze microstructure is not directly visible in the scanning electron microscope. Thus, an etching procedure using oxygen ions was employed to remove the plastically deformed layer at the sample surface. Control measurements on uncrazed samples showed that this procedure does not lead to artifacts. The surfaces were coated with gold to reduce surface charging. 

Secco 20 min without and Smin with ultrasonic agitation, reveals different types of defects and dislocations of different orientations, relatively poorly defined circular etch pits, requites ultrasonic agitation to minimize artifacts 319, 340. 387. 455... 

Figure 100. Partially stabilized Z1O2 ceramic, etched by thermal method at 1500 C for 1 h in air, SEM. Artifacts shown here are caused by thermal etching at excessive temperatures.

Once the sample has been polished to 3 pm, a final step (fine polishing) usually involving either an alumina slurry or colloidal silica slurry is used. The size of particles in these aqueous slurries can be as small as 0.02 pm. Once finished with this step, the sample is ready for etching. If elemental analysis of the polished sample is to be performed using SEM/EDS or other X-ray techniques, extra care should be taken. Often times artifact silicon or aluminum peaks can be introduced by accumulation of polishing abrasives in cracks and pores, and sometimes, depending on the metal hardness, by intrusion into the sample surface. 

A major difficulty in plasma and ion etching is that textures, such as steps, cones and holes, can be produced which are artifacts and which do not reveal the microstructure. Of all the methods of specimen preparation, etching is the most prone to such artifacts and thus image interpretation is very difficult. Etching preparations are useful for comparison with structures formed during other specimen preparation processes, especially microtomy. Such complementary studies are essential to the determination of the true polymer structure. 

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