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d
n
9
r
4
n
g
|
7
Figure 7.7
(a) Structure of Zeotile-4 material as established by discrete electron
tomography.
41
(b) Structure viewed along the main channels (pore size
8-10 nm). (c) Sideways view on the slit-like pores (pore size 2-4 nm).
.
Figure 7.8 Cross-sectional TEM images revealing the spreading of TiO
2
deposited in
a Zeotile-4 powder particle using 30 TDMAT/H
2
O ALD cycles and TDMAT
exposure times of 30, 90 and 300 s.
Adapted with permission from ref. 39. Copyright 2012 American
Chemical Society.
for ALD of TiO
2
using 30, 90 or 300 s exposure times. During the TDMAT
exposures, Ar was used as a carrier gas and the pressure in the ALD chamber
was ca. 0.15 Pa. In the first experiments using 30 and 90 s TDMAT exposure
times, the deposition temperature was 200 1C. For the 300 s sample, it was
necessary to reduce the deposition temperature to 120 1C in order to avoid
substantial decomposition of the Ti precursor. XRF characterization of the
samples confirmed a higher TiO
2
content with longer exposure times. TEM
images of coated powder particles oriented along the hexagonal main
channels of the Zeotile-4 structure are shown in Figure 7.8. The dark outer
rim observed in the TEM images is ascribed to the infiltration of TiO
2
ma-
terial in the slit-like mesopores of the Zeotile-4 structure (Figure 7.7). As in
the silica gel particle, the TiO
2
deposition front moved progressively deeper
into the powder particles with increasing TDMAT exposure time. The dark
rim measured ca. 20, 45 and 120 nm for 30, 90 and 300 s exposure,
respectively.
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