Regulating the composition, structure, and nanoscale dimensions of Yb₂Si₂O₇ environmental barrier coating to achieve a biomimetic teakwood-like functional structure by waste gas recycling

The unique multi-layer, multiscale structures of teakwood allow for excellent mechanical and long-term environmental stability, providing inspiration for the biomimetic design of the environmental barrier coating (EBC) structures. However, achieving the desired biomimetic structure control in high-temperature plasma spraying is a challenging task that requires new technological breakthroughs. In this study, a multi-scale nano Yb₂Si₂O₇-Yb₂SiO₅ (YbDS-YbMS) composite EBC with a teakwood-like lamellar structure has been realized by a novel alternating vapor/liquid phase deposition method in plasma spraying-physical vapor deposition (PS-PVD). Volatilized waste SiO₂ from Yb₂Si₂O₇ (YbDS) was reused and deposited on the coating surface during the spraying process, where a regularly arranged multi-layer structure was formed in the coating by the alternate deposition of gaseous SiO₂ and droplet YbDS. In addition, SiO₂ on the coated surface formed nanoclusters and dome-shaped nanocrystals by homogeneous and heterogeneous nucleation, respectively, and some of them gradually formed a continuous nanofilm as the arc current increased. The deposited SiO₂ reacted in situ with the decomposed phase YbMS in the coating to form YbDS preserved its multi-scale nanostructure after heat treatment, enabling the preparation of YbDS-YbMS composite coating. This work provides a new design strategy and method for the preparation of coatings using YbDS and other spray powders with similar decomposition and volatilization characteristics during plasma spraying process.