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 multilayer, multiscale structure of teakwood results in excellent mechanical and long-term environmental stability, providing inspiration for the biomimetic design of 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 multiscale nano Yb₂Si₂O₇–Yb₂SiO₅ (YbDS–YbMS) composite EBC with a teakwood-like lamellar structure was realized via a novel alternating vapor/liquid phase deposition method involving 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 multilayer 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 via 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, preserving its multiscale nanostructure after heat treatment and enabling the preparation of the 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 the plasma spraying process.