Sputtered metal carbide solar-selective absorbing surfaces

Abstract

A range of sputtered metal carbide interference filters has been prepared on copper substrates. These show promise as high-temperature-stable selective surfaces for solar energy photothermal conversion. Solar absorptances of 75%–80% and room temperature emittances of about 2% can be obtained at 300 K for single layer metal carbide films on bulk copper. The emittance of an iron carbide film on copper increased to 7% at 600°C. The solar absorptance of the same film was temperature independent up to 500°C. Absorptances of 80%–90% and room temperature emittances of about 4% can be obtained for two-layer interference filters on copper. The coating of both glass and metal surfaces is discussed.