Elemental Analysis of Contaminated Nuts

Elemental Analysis ofContaminated Nuts

Jeffrey W. ElamArgonne National Laboratory

Ossy performed a high-temp vacuum bake of a frit-sealed glass base and sidewall

After the bake, there was contamination in the chamber – black deposits.

Ossy shipped contaminated nuts, along with clean nuts, to ANL for analysis

Jeff did EDAX (energy dispersive analysis of X-rays) in the SEM.

Background:

2

Clean Contaminated with black residue

Nuts mounted to SEM stage using carbon tape

3

SEM images of clean nut:

This entire field of view used for EDAX in the following slide

4

EDAX of clean nut

Detail showing nice fit to Ag, Sn region (blue line) indicating we have only the elements indicated

5

EDAX of clean nut

Neglecting the surface carbon contamination (I see this on virtually every sample unless I plasma clean) the clean nut is almost entirely Ag. Makes sense since it’s been silver coated.

6

SEM images of dirty nut:

This entire field of view used for EDAX in the following slide

This patch is covered with white spots – I think this is one of the dark regions in the photo on slide 2

7

EDAX of dirty nut

We see new elements on the dirty nut: Cu, Bi, Sn, Cr, Fe.We don’t see any Pb.The Cr and Fe might come from the steel.To me, the Bi is the most suspicious.

8

More SEM, EDAX of dirty nut

Zoom in SEM so one of the white spots in slide 7 is now the entire field of view

Bi

Neglecting carbon, the white spots are mostly Bi9

Conclusion: the white spots in SEM (which are the black residue observed by eye) are mostly bismuth.

Is there bismuth in the frit?

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