Chemical, structural and optical characterization of a black chrome solar selective absorber

Technical Report · Sun Jul 01 04:00:00 EDT 1979

OSTI ID:5814956

Lampert, C M

The very popular black chrome coating, Harshaw Chemical's Chromonyx was analyzed in terms of materials science to determine the nature of its microstructure and relationship to wavelength selectivity. This coating serves as an efficient solar thermal conversion coating for both concentrating and flat plate solar collectors. General properties of solar energy and selective absorbers are discussed to give a firm footing for analysis. Also, the properties and degradation modes were revealed for samples heat treated at high temperatures for short times. Several electrodeposited black chrome-substrate combinations were investigated including the favored black chrome with a dull nickel underlayer. It was found that black chrome coating thickness and surface roughness greatly influence spectral hemispherical reflectance. To a minor extent underlayer material also altered infrared reflectance; nickel, copper and steel were evaluated. Principally, energy dispersive x-ray analysis as well as scanning and transmission electron microscopy were employed for thin film analysis. The microstructure of the as prepared and annealed coating up to 300/sup 0/C consists of agglomerated 0.05 to 0.3 micron size particles with chiefly an oxide surface. Suspended within these oxide particles are 140 A (average size) metallic chromium grains. The volume ratio of chromium to oxide increases with depth, finally forming a metal rich region at the substrate interface. Effective medium theories are discussed briefly to describe mathematically the coating's solar selectivity. Microstructural analysis was performed on 1 to 100 hour annealed specimens over the temperature range of 300 to 600/sup 0/C, in atmospheres of air and medium vacuum.

• Research Organization: California Univ., Berkeley (USA). Lawrence Berkeley Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5814956
• Report Number(s): LBL-9123
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
141000* -- Solar Collectors & Concentrators
ABSORPTIVITY
AUGER ELECTRON SPECTROSCOPY
BLACK CHROME
BLACK COATINGS
CHALCOGENIDES
CHEMICAL REACTIONS
CHROMIUM
CHROMIUM COMPOUNDS
CHROMIUM OXIDES
COATINGS
CRYSTAL STRUCTURE
DEPOSITION
ELECTRODEPOSITION
ELECTROLYSIS
ELECTRON MICROSCOPY
ELECTRON SPECTROSCOPY
ELECTROPLATING
ELEMENTS
EMISSIVITY
HEAT TREATMENTS
LYSIS
MATHEMATICAL MODELS
METALS
MICROSCOPY
MICROSTRUCTURE
OPTICAL PROPERTIES
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PLATING
SCANNING ELECTRON MICROSCOPY
SOLAR ABSORBERS
SOLAR COLLECTORS
SPECTRAL REFLECTANCE
SPECTRALLY SELECTIVE SURFACES
SPECTROSCOPY
STABILITY
SURFACE COATING
SURFACE PROPERTIES
SURFACES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS