Fabrication of ultra-black carbon nanotube absorber based on hot-air assisted spray

Due to their exceptional light absorption capabilities, ultra-black materials have gained significant importance in various fields, such as aerospace, energy harvesting, and seawater desalination. However, the existing methods for producing ultra-black materials involve high-temperature processes, which limits their practical applications. In this study, we present a novel approach that utilizes hot air to facilitate the formation of coating surface microstructures using carbon nanotube (CNT) slurry. This method enables the large-scale production of ultra-black materials at room temperature. Experimental results demonstrated the successful preparation of the coating, allowing for the direct exposure of the surface microstructure of the CNTs. Morphological characterization revealed the acquisition of a porous microstructure after spraying, resulting in more light-scattering sites. These porous structures and light scattering sites play a vital role in achieving superior light absorption, with the coating demonstrating an average light absorption rate of up to 99.51%. Furthermore, the superior light absorption improved the heat collection capabilities of the coating, enabling rapid heating to 94.8 °C within 10 s. This innovative process overcomes the drawbacks of existing methods for ultra-black material preparation, opening new possibilities for large-scale ultra-black material preparation and application at room temperature.