• Oliveira, Ac
• Coelho, B.
• Simao, Ra
• Teixeira, Rlp
• Raniero, L.

Abstract

A low-cost, black nickel solar absorber coating, to be used in thermal solar collectors on nanostructured highly thermal conductor copper, was analyzed using the thermoanalytical flash method at 293 K and Cernuschi's two-layer models, to identify the thermal properties of the blackening layers and the energy losses connecting different parameters such as the chemical composition, diffusivity, conductivity, and emittance. The Cernuschi's modelling presents a good approximation of the experimental results. The black nickel layer has low thermal losses, an estimated specific heat of 390 J/(kg K), a thermal conductivity of 105.1 W/(m K) and a thermal diffusivity of 39.4 × 10. -6 m. 2/s. The black nickel layer has low optical losses and an emittance of 0.09 (293 K), but its thermal stability ends at 473 K, indicating that black nickel above 473 K is not stable and a structure change may occur. Chemical analysis shows that nanostructured black nickel is a cermet mainly composed of two metallic nickel atoms for each nickel and zinc sulphide, i.e. 2 Ni. 0: NiS: ZnS.

Topics

• impedance spectroscopy
• nickel
• zinc
• chemical composition
• copper
• diffusivity
• thermal conductivity
• specific heat