Solar selective black cobalt: preparation, structure, and thermal stability

Journal Article · Fri Aug 01 00:00:00 EDT 1980 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.328276· OSTI ID:5265169

Smith, G B; Ignatiev, A; Zajac, G

In the quest for an electroplated selective black coating stable to 500 /sup 0/C in air, black cobalts have been prepared by three techniques to yield (a) plated cobalt sulphides, (b) plated cobalt oxide-hydroxide, and (c) cobalt oxide prepared by thermal oxidation of electropolated cobalt metal. The optical properties of the various coatings are analyzed before and after exposure to air for extended periods of time at temperatures in the 300 /sup 0/--500 /sup 0/C range. The sulfide black cobalt is not acceptable as a high-temperature selective absorber due to severe thermal degradation. The plated oxide is a good selective absorber to about 400 /sup 0/C, and the thermally oxidized black to a slightly higher temperature, but degrades at 500 /sup 0/C. Structure studies via scanning electron microscopy (SEM), Auger electron spectroscopy (AES), and x-ray photoemission spectroscopy (XPS) are reported which yield a full account of the coating chemistry before and after heating. The studies reveal that the high solar absorptance of the acceptable black cobalt coatings is due to a continuation of a porous outer layer grading into nondense oxides of cobalt; either CoO or Co/sub 3/O/sub 4/, depending on the film. Absorption is intrinsic but not due to metal particles as in black chrome. A limited amount of optical degradation occurs upon heating the oxide black cobalt in air due to oxidation of hydroxide. However, the major degradation problem is shown to be substrate oxidation in contrast to black chrome where film oxidation is the principal problem.

• Research Organization: Department of Physics, University of Houston, Houston, Texas, 77004
• OSTI ID: 5265169
• Journal Information: J. Appl. Phys.; (United States), Vol. 51:8
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
BLACK COATINGS
COBALT SULFIDES
SOLAR RADIATION
ABSORPTION
AUGER ELECTRON SPECTROSCOPY
COBALT COMPOUNDS
COBALT HYDROXIDES
COBALT OXIDES
DATA
ELECTRON MICROSCOPES
ELECTRON SCANNING
FABRICATION
HIGH TEMPERATURE
MECHANICAL PROPERTIES
OPTICAL PROPERTIES
STABILITY
SURFACES
THERMAL DEGRADATION
THERMODYNAMIC PROPERTIES
CHALCOGENIDES
COATINGS
ELECTRON SPECTROSCOPY
HYDROGEN COMPOUNDS
HYDROXIDES
INFORMATION
MICROSCOPES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RADIATIONS
SPECTROSCOPY
SULFIDES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
140501* - Solar Energy Conversion- Photovoltaic Conversion