Sol-Gel Process in the Synthesis of Cobalt Based Metal Oxides as Solar Selective Absorber Thin Film Coatings for Photothermal Collector
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Date
2016-02-25
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Abstract
Cobalt-based metal oxide thin film coatings have been successfully deposited on
highly reflective aluminum substrates via sol–gel dip-coating process. The coating’s surface
composition, surface topography and morphology as well their optical properties were
probed using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM),
scanning electron microscopy (SEM), and UV-Vis-Nir spectrophotometry, respectively.
The XPS spectra indicated that the coatings contained the mixed cobalt based metal oxides.
Topographical and morphological investigations showed that the copper-cobalt oxide
coating had the roughest surface with contour in range of 120 nm compared with other two
coatings. The copper cobalt oxide coatings also exihibed a distinct optical property and
behaved as solar selective absorber. Variation in withdrawal rate and dip-drying cycles
confirmed that the copper cobalt thin film coating had a very tuneable absorptance value
with the highest absorptance (α=80.2%) was achieved when the coating was created using
six times dip-drying cycles with the withdrawal rate of 120 mm/min. Simplicity and safe in
the synthesis process as well as the optical features of the copper–cobalt coatings imply
good prospects for future application as a solar absorber coating material for photothermal
collector application, though they still need further engineering to improve optimal
performance.
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Keywords
cobalt based metal oxide, dip-coating, solar selective absorber, sol-gel, surface