3.3. SEM–EDX study
In fundamentally oriented studies and atomization mechanism
explanation, the physico-chemical transformations of the permanent
modifier introduced into the graphite furnace are of interest. In this
study, the multi-method experimental approach consisting of
scanning electron microscopy investigations with secondary electron
(SE) as well as backscattered electron imaging (BSE) and energy
dispersive X-ray detection EDX are presented. Investigations of the
phenomena related to the modified graphite surfaces were performed
by comparing – in SEM–EDX studies – the pyrolytically coated L'vov
platform freshly modified by Ir/Nb and platform after about 200
firings of soil and sediment slurries. The L'vov platform modified by Ir/
Nb was prepared as described in Section 3.1 and cut with EM UC7
ultramicrotome (Leica Microsystems (Schweiz) AG, Heerbrugg,
Switzerland). The properly cut pieces were cleaned by dry air stream
blown onto the surface and the broken samples were fastened to the
sample holder by carbon taps, which are sticky on both sides. Since
the samples were well electrically conductive, coating with gold or
carbon was not necessary. In this way, there was no interference of
the coating with elemental spot analyses carried out with the energy
dispersive X-ray EDX detector. Then, pyrolytically coated L'vov
platform freshly modified by Ir/Nb and platform after about 200
firings were examined by SEM–EDX in order tofind the changes of the
graphite structure. Images were derived from the secondary electrons
(SE) and backscattered electrons (BSE). Fig 3presents an example of a
SE image of a pyrolytically coated L'vov platform freshly modified by
Ir/Nb at magnification of ×1200. The micrograph shows that Ir and Nb
are formed cauliflower-like structures on the pyrolytic graphite
coating [22] and that modifiers are not distributed homogenously
on the entire L'vov platform surface.