Sol-gel protective coatings for black chrome solar selective films

Conference · Thu Jan 01 04:00:00 EST 1981

OSTI ID:5921857

Pettit, R B; Brinker, C J

Electrodeposited black chrome solar selective films degrade rapidly when heated to temperatures above 300/sup 0/C in air. The application of sol-gel protective coatings to the black chrome films has been investigated as a possible means to improve the oxidation resistance of black chrome at high temperatures. The sol-gel coating process consists of applying an alcoholic solution containing polymeric glass precursors. After the coating is fired for about one-half hour at a moderate temperature (approx. 450/sup 0/C), a glass layer is obtained. Because of the wide range of sol-gel processing parameters, initial studies have concentrated on determining the effect of the following variables on the thermal stability of sol-gel coated black chrome: (1) sol-gel composition; (2) firing temperature; (3) firing atmosphere; (4) sol-gel coating thickness; and (5) pre-aging of the black chrome films. Of the compositions studied, only SiO/sub 2//B/sub 2/O/sub 3/ and SiO/sub 2//B/sub 2/O/sub 3//Al/sub 2/O/sub 3//Na/sub 2/O/BaO resulted in improved thermal stability. Of the other processing parameters, the firing temperature had the most significant effect on the resulting black chrome thermal stability, with 500/sup 0/C firing being optimum. For the best combination of process variables studied to date, the solar absorptance of a sol-gel coated sample decreased from 0.97 to 0.95 after 100 hrs at 400/sup 0/C, while, for an uncoated control sample, the solar absorptance decreased to 0.89. For most of the sol-gel coated films, continued aging at 400/sup 0/C resulted in continued protection of the black chrome film.

• Research Organization: Sandia National Labs., Albuquerque, NM (USA)
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 5921857
• Report Number(s): SAND-81-1889C; CONF-820107-1; ON: DE82004138
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
141000* -- Solar Collectors & Concentrators
ABSORPTIVITY
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
ATMOSPHERES
BARIUM COMPOUNDS
BARIUM OXIDES
BLACK CHROME
BLACK COATINGS
BORON COMPOUNDS
BORON OXIDES
CHALCOGENIDES
CHEMICAL COMPOSITION
COATINGS
CONCENTRATING COLLECTORS
CONTROLLED ATMOSPHERES
DEPOSITION
DIMENSIONS
ELECTRODEPOSITION
ELECTROLYSIS
EQUIPMENT
FILMS
HEAT TREATMENTS
LYSIS
OPTICAL PROPERTIES
OXIDES
OXYGEN COMPOUNDS
PARABOLIC COLLECTORS
PARABOLIC TROUGH COLLECTORS
PHYSICAL PROPERTIES
PROTECTIVE COATINGS
SILICON COMPOUNDS
SILICON OXIDES
SODIUM COMPOUNDS
SODIUM OXIDES
SOLAR COLLECTORS
SOLAR EQUIPMENT
SPECTRALLY SELECTIVE SURFACES
STABILITY
SURFACE COATING
SURFACES
TEMPERATURE EFFECTS
THERMAL DEGRADATION
THICKNESS