Formation and performance of highly absorbing solar thermal coating based on carbon nanotubes and boehmite

A major component of solar thermal systems is the solar absorber, which converts light into heat. We report on achieving high absorptance, excellent adhesion, and high thermal stability of carbon nanotube-based black coatings by applying a layer of Boehmite (AIOOH) on top of the carbon nanotube (CNT) film by solution-processed spray deposition. The CNT layer made-up by spraying, functions as an absorbing layer and the AIOOH serves as an anti-reflecting and protecting film. The anti-reflecting property of AIOOH layer effectively increases the absorptance of CNT coating by decreasing the reflectance. The effect of the thickness of AIOOH layer on the absorptance, adhesion, and thermal stability of the resulting CNT/AIOOH coating was investigated. The CNT/AIOOH coating with optimized thickness of AIOOH layer shows very high absorptance (alpha) of 0.975. The adhesion of the coating is in the range of 95-100% with significant increase of thermal stability. This new approach is expected to open new possibilities for fabricating low-cost, highly efficient and thermally stable solar-thermal devices which are based on simple coating processes. (C) 2016 Elsevier Ltd. All rights reserved.