Biomedical Engineering Reference
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°
at 500
C with a corresponding compression of ∼40%. High
magnification views of the array after UV-ozone (low temperature)
removal of the PFS template (Fig. 2.20b), or high temperature
annealing (Fig. 2.20e), allow comparison with the simulated
compression from the cubic lattice. Simulated projection matches
to the nonannealed and heat annealed sections show a 14% and
48% vertical compression, respectively, both aligned with the (211)
lattice direction.
February 8, 2010 17:21
(a)
(b)
(c)
(d)
(e)
(f)
[111]
Direct observation of vertical compression in the gyroid
structure after 500
Figure 2.20
.
(a, d) Cross-sectional views of the gyroid template electrochemically filled
with Ti(IV) oxide before and after annealing at 500
°
C crystallization of Ti(IV) oxide into anatase TiO
2
°
C for 2 h. The film
thickness compression in (d) is ∼40%. (b) Magnified view of the network
after low temperature UV-ozone template removal. (e) Magnified view
of the compressed network in (d). (c) Simulated (01
1) projection with
14% compression in (211) direction. (f ) Simulated (01
1) projection with
50% compression in (211) direction. Image size in (b-f ) 200 nm, 50 nm
simulation unit cell size. Reproduced with permission from Ref. [61].
The source of compression in the replicated network is a
volume contraction of the electrochemically deposited material on
heating. This is confirmed by thickness measurements of flat films
(Fig. 2.22) before and after high temperature processing. Since the
film cannot shrink in the lateral direction (without fracturing from
the substrate), all compression is taken up by vertical compression.
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