3.6. Scanning electron microscopy (SEM)
The morphological features of solid material is important to
study the geometry structure, pattern and particle shape on it’s
solid surface. SEM images of all samples, CS-CaO, STD nanoCa(OH)2
and surfactant-hydration treated Ca(OH)2 before and after
calcination at 400 C were shown in Fig. 5. The morphology of combusted
clamshell (CS-CaO) showed an agglomeration structure of
particles demonstrating sintering of the metal oxides during high
heat treatment (800 C) [57]. Besides, the pattern of CS-CaO was
presented in irregular shape with large aggregate forms (Fig. 5a).
The surfactant-hydration treated Ca(OH)2 showed significant
reduction in particle shape compared to STD nano-Ca(OH)2. The
STD nano-Ca(OH)2 appeared in finer and smaller uniform size of
aggregated round shape particles (Fig. 5b). Different morphology
and pattern was observed for treated samples under different type
of surfactants (EG, DE, and CTAB). EG surfactant treated-Ca(OH)2
significantly showed new formation of flower crystal structure on
Ca(OH)2 (Fig. 5c), while DE surfactant treated-Ca(OH)2 was
observed in cube-like shape with layers assembled to form a large
particle (Fig. 5d). Morphology of the CTAB surfactant treatedCa(OH)2
was presented in the form of irregular shape with rough
surface (Fig. 5e). The nanostructure of each surfactant treated catalysts
was slightly agglomerated from original pattern after subsequent
thermal treatment at 400 C (Fig. 5c1–e1). The SEM images
showed that crystal structure of catalysts were marginally bigger
in shape after heat treatment, which indicated that surfactants
are able to control and restrain particles growth rate from sintering
during calcination process.
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