Scanning electron microscopy sample materials

The consolidated titanate waste pellets are similar in appearance to their glass counterparts, i.e., both are dense, black and apparently homogeneous. Microscopic analyses, however, reveal important differences between these two waste forms. While little definitive work has been done with glassy waste forms, it is apparent that several readily soluble oxide particulates of various nuclides are simply encapsulated in the glass matrix. The titanate waste form has undergone extensive analyses which includes optical microscopy, x-ray, scanning electron microscopy, microprobe, and transmission electron microscopy (l ) The samples of titanate examined were prepared by pressure sintering and consisted of material from a fully loaded titanate column. Zeolite and silicon additions were also present in the samples. 

Scanning electron microscopy is an important tool when examining the mode of wear of any sample. The surface of the sample is coated with a very thin layer (only several atoms thick) of a conductive material such as gold. The surface is scanned using a beam of electrons and the image magnified and recorded. 

The oldest microscopy technique for materials analysis was optical microscopy. Even to this day, for feature sizes above 1 pm, this is one of the most popular tools. For smaller features, electron microscopy techniques such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are the tools of choice. A third family of microscopy includes scanning probe tools such as scanning tunneling microscopy (STM) and atomic force microscopy (AFM). In these relatively recent techniques, sample preparation concerns are of minor importance compared to other problems, such as vibration isolation and processing of atomically sharp probes. Therefore, the latter techniques are not discussed here. This chapter is aimed at introducing the user to general specimen preparation steps involved in optical and electron microscopy [3 7], which to date are the most common... 

For scanning electron microscopy of electrically insulating materials, the surface of the specimen may be electrically isolated when bombarded with electrons. This leads to charge buildup on the specimens that makes imaging or other analysis difficult. To address this issue, special sample coating steps are often required and have been discussed in Section 9.2.3. 

Evidence which seems to favour the original model of Alzamora et al. is provided in a recent paper by Doesburg et al.74 In this, samples of coprecipitated material, precipitated at pH 7 from a mixture of nitrates with a Ni/Al ratio of 2.33 (xNi = 0.7) were examined by scanning electron microscopy after coprecipitation, after calcination at 600 °C in air, after reduction in H2... 

---