A Bi-Layer Plasma Sprayed Alumina for Optical Application

Materials with fine-scale structures are recognized to exhibit technologically efficient mechanical or thermal properties. Thermal sprayed nanostructured media could also be interesting in the optical field thanks to the diffusion interaction between short wavelength radiations and submicronsized pores.

One difficulty of Suspension Plasma Spray (SPS) is to provide a coating enough thick and to keep efficient mechanical properties when the coating is removed on his substrate.

The aim of this study is to spray a reflective and diffusive self-supporting bi-layer alumina : the first coating is obtained by Atmospheric Plasma Spraying of micron powders in order to reach an enough thickness and the second one is sprayed by SPS on the first one with strong adherence. An oxide ceramic material with high diffuse reflectivity in a large band of wavelengths is obtained.

Investigations about mechanical and adherence properties between the two layers are presented.