Biomedical Engineering Reference
In-Depth Information
Fig. 6.17
SEM images of CaCO
3
films crystallized from ACC films on SAFs in the environment
with the desired density of anhydrous ethanol: (
a
) as-deposited, (
b
)1h,(
c
)2.5h,(
d
)4h.
(Reproduced from [
105
], Copyright © 2009, Wiley)
6.3.5
The Role of Solvent during Transformation Process
Shen and co-workers demonstrated that organic solvent has profound influence on
transformation of ACC thin films (Fig.
6.17
)[
106
]. It is a simple method to prepare
polymorphic CaCO
3
crystal from the ACC by controlling the crystallization process.
The model organic templates are introduced to obtain the ACC thin films and the
organic media is used to control the transformation of CaCO
3
. Interestingly, using
anhydrous ethanol as media, ACC quickly transformed, probably by dissolving
and recrystallizing, to calcite and vaterite after maturing. The experiment results
indicated that the medium anhydrous ethanol facilitated the transformation of ACC
and had an obvious effect on the morphology of the CaCO
3
crystals. Their results
point out that a metastable ACC thin film was a precursor to the two polymorphs,
calcite and vaterite, when organic solvent ethanol was used as media. During the
process, the interactions between the surface of ACC film and ethanol molecule
is exist. And the ethanol molecules are preferential to combine water molecule of
calcium-enriched surfaces of the film to trigger the transformation.
