Phase composition and microstructure of silicon coatings deposited by air plasma spraying

Silicon coatings were deposited using air plasma spraying technology. The phase composition and microstructure of the coatings were examined by X-ray photoelectron spectroscopy, X-ray diffraction, wavelength-dispersive X-ray spectrometry, field emission scanning electron microscopy and transmission electron microscopy. The results showed that the surface of the as-sprayed silicon coating was almost covered by submicronic particles mainly composed of silicon oxide. Much less oxide was detected in the interior of the coating than that of the surface, which was explained on the evaporation of silicon oxide during plasma spraying because of the tiny difference between its boiling and melting points. The coating exhibited lamellar structure. Lots of silicon grains with different sizes and irregular shapes appeared in the coating. Nanoscale grains were also observed in the coating.