Sprayable reduced graphene oxide based high‐temperature solar absorber coatings for concentrated solar power applications

Reduced graphene oxide (RGO) based composite non-selective solar absorber coatings (RGO/silicate) were developed using a simple spray technique. RGO powders were prepared using the modified Hummers' method. RGO-silicate suspensions were obtained by adding an appropriate quantity of RGO in a sodium silicate solution. Transmission electron microscopy studies showed the corrugated morphology of reduced graphene oxide powders. The presence of RGO in the composite absorber coatings was confirmed by X-ray photoelectron spectroscopy data. In order to study the thermal stability, the coatings were deposited on stainless steel (SS) and Inconel substrates. The composite nonselective coating exhibited an absorptance (α) of 0.96 and emittance (ε) of 0.88 at 82°C on SS and Inconel substrates. The coatings sprayed on SS substrates showed good thermal stability for 428 hours at 500°C in air. The coatings sprayed on Inconel substrates were thermally stable in air at 600°C for 96 hours. The performance evaluation tests revealed that these coatings can be used for concentrated solar power applications.