SPUTTERED METAL CARBIDE AND METAL SILICIDE SOLAR ABSORBING SURFACES

Thin transition metal films reactively sputtered in Ar + CH4 or Ar + SiH4 show promise as solar selective absorbers that are stable at high temperatures in vacuum. An examination of the structure of these films shows that they consist of closely packed metallic particles that are electrically isolated from each other as in cermets. The optical properties of reactively sputtered Fe-C films are discussed. Multilayer and graded films produced by reactive sputtering can show considerably better absorptances than equivalent uniform films without their thermal emittances being seriously affected. Solar absorptances of 0.90-0.95 are routinely achieved, films with these absorptances having room temperature emittances of 0.03-0.04. However, degradation of the films may occur at high temperatures and may lead to changes in their solar absorptances. © 1979.