Manufacture of Reflective Aluminium Surfaces Using Cold Spray

Abstract

This research demonstrates the use of cold spray (CS) as an additive manufacturing process to manufacture reflective aluminium coatings. Nitrogen was used as a carrier gas at various gas heating temperatures. Following deposition, the coatings were finished using a number of machining and/or polishing processes to surface roughness values of 20-150 nm. The samples were characterised with respect to total reflectivity within the wavelength range of 400-1800 nm, porosity, surface roughness, and density. The reflectivity of the coatings approached that of bulk material, and 99% dense coatings were obtained. Increasing the gas heating temperature did not decrease the porosity with the lowest gas heating temperature found to deliver the best reflectivity. This work demonstrates that CS can be used to coat thin layers of aluminium onto various materials, which can be subsequently polished to create composite reflectors. This provides a novel reflector with the reflectivity of aluminium, and the structural and thermal properties of the substrate material, allowing for greater flexibility in the manufacture of reflectors.