PNNL-13501 - Pacific Northwest National Laboratory

Figure 5. Close-up atomic force microscan scan of Figure 4
showing crystalline terraces that compose the large crystal
Figure 6. Atomic force microscopy scan of the dendrites just
to the right of the large crystal in Figure 3
Figure 7. Atomic force microscopy scan of the surface of a
dendrite shown in Figure 6
Summary and Conclusions
A sample of Np(V) deposits on the cleavage surface of
single crystal calcite was prepared, and the surface
imaged both optically and by atomic force microscopy.
These images indicated that Np(V) forms both thick
crystals and thinner dendrites under a deposition process
that may be similar to that found in the vadose zone.
Both large crystals and dendrites showed a preferred
orientation, suggesting some alignment with the
underlying calcite crystal structure. The project
demonstrated our ability to collect data relevant to vadose
zone and groundwater contaminant transport issues.
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