Superhydrophobic polytetrafluoroethylene film deposited on solar selective absorber by electron beam evaporation

Polytetrafluoroethylene (PTFE) film has been deposited on solar selective absorber (SSA) by electron beam evaporation. The water contact angle of the SSA surface after coating with PTFE (called PSSA) has increased from 72° to 150°, indicating that the surface has changed from hydrophilic to superhydrophobic. The absorptance of the SSA was 92.91% after coating with PTFE, while the emittance of the SSA was slightly increased due to the absorption of PTFE material itself. The color difference of SSA before and after coating with PTFE was small because of the high transmittance of PTFE film. In addition, the self-cleaning tests via water droplets of SSA and PSSA show that SSA has significant self-cleaning property after coating with PTFE. The results can provide reference for superhydrophobic coating applied to solar thermal fields.