Diagram of the home-built ALD reactor.
SEM images of (a) carbon fibers before thin film deposition; (b) coated carbon fibers with alumina by sequential exposure to aluminum chloride and water vapor; (c) and (d) ends of single coated carbon fibers.
SEM images of carbon fibers coated with alumina by sequential exposure to trimethylaluminium and water; the purge time increases from 15 s [images (a)–(c)] to 30 s [images (d)–(f)] to 45 s [images (g)–(i)]. Intermediate magnifications (b), (e), and (h) indicate that the film becomes more homogenous with increasing purge times.
(Color online) Film thickness as a function of the number of deposition cycles using 15 s, 30 s and 45 s purge time, respectively. Each data point represents the average of at least 20 individual fibers.
TEM image of a cross-section trough a single fiber coated with Al2O3.
SEM images of titania coated carbon fibers (a) rough (15 s purge time) and (b), (c) conformal surface (40 s purge time).
(a) and (b) SEM overview images of carbon fibers coated with 200 cycles of Al2O3 and 300 cycles of TiO2, (c) cross-sectional TEM image of a coated fiber. Image (c) is reproduced with permission from A. K. Roy, S. Schulze, M. Hietschold, and W. A. Goedel, Carbon 50, 761 (2012).
(Color online) Elemental analysis of a carbon fiber coated by a double layer of alumina and titania obtained by EDXS. Selected area for measurement is marked by a black frame in the image on the left picture. EDXS spectrum on the right shows that there are signals from five elements present. The copper signal is an artifact due to the sample holder. Aluminum, titanium, and oxygen are strong—in agreement with the expected chemical composition of the coating. A small chloride signal presumably is due to an incomplete hydrolysis of the precursor.
TEM overview image of (a) alumina microtubes (b) titania microtubes, and (c) alumina/titania microtubes prepared from coated carbon fibers via oxidation in air at 550 °C.
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