The morphology of the wollastonite prepared by CaO
from eggshell and SiO2 from diatomite using the
hydrothermal method with and without calcination at
800 oC is shown in Fig. 1 and Fig. 2, respectively. The
SEM results indicate that the particles of wollastonite
agglomerated into small particles sized more than 1 μm
when they were not calcined. In contrast, they had a
clear shape when calcined with the size of 0.3 μm
(width) × 2 μm (length) obtained under hydrothermal
method at 100 oC (Fig. 2(a)). The size of the particle