Evaluation of vacuum deposition-sputter deposited cermet selective absorber coatings. Final report, January 15, 1980-November 30, 1982

Technical Report · Fri Dec 31 00:00:00 EST 1982

DOI:https://doi.org/10.2172/5059468· OSTI ID:5059468

Thornton, J. A.; Lamb, J. L.

In a preliminary investigation at Cornell University it was shown that Pt/Al/sub 2/O/sub 3/ cermet coatings with graded Pt composition profiles could be deposited by co-evaporation in forms that yielded excellent selective absorber properties and thermal stability at 600/sup 0/C in air. The co-evaporation method is difficult to apply to the variety of substrates that are of interest for medium and high temperature solar thermal receivers. Accordingly, this project was undertaken to investigate the use of sputtering. Three coating configurations were examined: (1) cermets with graded Pt compositions and Al/sub 2/O/sub 3/ antireflection layers; (2) cermets with uniform Pt compositions and Al/sub 2/O/sub 3/ antireflection layers; and (3) Al/sub 2/O/sub 3/-M-Al/sub 2/O/sub 3/ type coatings with Pt/Al/sub 2/O/sub 3/ M-layers. Sputter co-deposition was used to form the cermet layers. Direct rf sputtering of alumina and dc reactive sputtering of aluminum were investigated as methods for depositing the Al/sub 2/O/sub 3/. The rf sputtered Al/sub 2/O/sub 3/ was found to yield coatings with superior thermal stability. Thus, when deposited with re-sputtered Ak/sub 2/O/sub 3/ onto Pt base layers at elevated temperatures, all three of the coating configurations listed above were stable in air at 600/sup 0/C. Absorptances were in the range 0.90 to 0.95. The graded cermet coatings appear to be the generally most useful of the three types examined. Optimized coatings on Pt coated glass substrates have yielded absorptances of 0.97 and room temperature emittances of about 0.08. Alternative ir reflector layer materials such as Cr, Mo, Ta, W and ZrB/sub 2/ were investigated and concluded to be limited to low temperature (approx. 400/sup 0/C) applications. Substrate surface polishing is concluded to be an important consideration affecting the optical properties and thermal stability of coatings. Experiments are described in which 24 inch long receiver tubes were coated with Pt/Al/sub 2/O/sub 3/ graded cermet coatings by sputtering.

• Research Organization: TELIC Corp., Santa Monica, CA (USA)
• DOE Contract Number: AC02-77CH00178
• OSTI ID: 5059468
• Report Number(s): SERI/TR-8260-1-T1; TELIC-82-4; ON: DE83014482
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
SOLAR RECEIVERS
SPECTRALLY SELECTIVE SURFACES
SPUTTERING
ABSORPTIVITY
ALUMINIUM OXIDES
CERMETS
EMISSIVITY
INCOLOY ALLOYS
MICROSTRUCTURE
PLATINUM
SPECTRAL REFLECTANCE
STABILITY
STAINLESS STEELS
SUBSTRATES
ALLOYS
ALUMINIUM COMPOUNDS
CHALCOGENIDES
CHROMIUM ALLOYS
COMPOSITE MATERIALS
CORROSION RESISTANT ALLOYS
CRYSTAL STRUCTURE
ELEMENTS
EQUIPMENT
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
IRON ALLOYS
IRON BASE ALLOYS
MATERIALS
METALS
NICKEL ALLOYS
OPTICAL PROPERTIES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PLATINUM METALS
SOLAR EQUIPMENT
STEELS
SURFACE PROPERTIES
SURFACES
TRANSITION ELEMENTS
141000* - Solar Collectors & Concentrators