Geoscience Reference
In-Depth Information
Figure 10.19 Fine crystals of zirconia and ceria.
Source: Photographs by M. Yoshimura.
ceria
zirconia solid solutions (Zr
0.5
Ce
0.5
O
2
). A clear solution of 0.2 M Ce(NO
3
)
3
and ZrO(NO
3
)
2
was treated hydrothermally at 120
C for 6 h in the higher pH region
(
zirconia solid solution
nanoparticles
[103]
. The most significant aspect of these reports is the much lower
temperature of ceria nanoparticles processing compared to the earlier published
literature data and also without any additional external energy source or sophisti-
cated equipment. A simple soft chemical processing route has been employed here.
When ball milling was employed to the hydrothermal technique in the preparation
of ceria
9.0).
Figure 10.21b
shows the TEM photographs of ceria
.
zirconia nanoparticles, the particles size was further reduced.
It is interesting to note that the structural, optical, electronic, and catalytic prop-
erties of ceria nanocrystals are strongly dependent on their crucial geometrical
parameters like size and shape. Therefore, the preparation of high-quality ceria
nanocrystals with desired morphology is of great fundamental and technological
interest. Adschiri and Arai have done extensive work on the supercritical hydro-
thermal synthesis of ceria particles
[41,104,105]
.
Figure 10.22a and b
shows typical
ceria particles obtained under subcritical and supercritical conditions. As it could be
seen from
Figure 10.22a and b
, the ceria particles crystallized under subcritical condi-
tions are larger than the ceria particles obtained under supercritical conditions
[106]
.It
was also confirmed by these authors that the rise in experimental temperature and
experimental duration influence on the particle size. At subcritical conditions, particle
size varied with the reaction time even above conversions of 95%. The contribution of
the residual 5% of ion to the particle growth is negligibly small. The growth of the
