Résumé
Efficient photo-thermal solar collectors are growing in importance to limit the use of fossil fuels. For the conception of tandem absorber, different carbon nanotubes, with highly UV-Vis-NIR absorbing, are deposited onto a highly IR reflecting metalized substrate by electrophoretic deposition. In order to guarantee an eco-friendly process, the nanotubes are dispersed in an aqueous solution by purple pyrocatechol. This molecule confers an electric charge to the colloids, while ensuring an electrostatic repulsion. Then, the zeta potential of the colloids is determined to evaluate the stability of the suspensions. The optimal formulation shows no settling for several days. Tandem absorber are obtained by varying different EPD parameters (deposition time, applied potential, inter-electrode distance) in order to control the final thickness, density, morphology of the film and so to tune the absorbance and the reflectance of the tandem absorber. To improve the performance and durability of the deposits, post treatments such as the addition of an antireflective layer or annealing are performed. It is possible to convert more than 90% of the absorbed light into heat, limit the thermal losses (<10%) and guarantee a mechanical stability of the coatings up to 350°C.