Design and fabrication of pyrolytic carbon-SiC-fluoridated hydroxyapatite-hydroxyapatite multilayered coating on carbon fibers

A multilayered coating of pyrolytic carbon-SiC-fluoridated hydroxyapatite-hydroxyapatite (PSFH) was designed and synthesized on carbon fibers (CF) by a combined method composed of chemical vapor deposition and pulsed electrochemical deposition. The morphology, microstructure, chemical composition and wettability of the coating were characterized. The formation mechanism of PSFH coating was discussed. The in-vitro bioactivity and corrosion behavior in simulated body fluid (SBF) were tested. PSFH coating exhibited a multilayered core-shell structure consisting of pyrolytic carbon layer, SiC layer, fluoridated hydroxyapatite layer and hydroxyapatite layer. The coating was dense and crackfree attributing to gradient thermal expansion coeficient. The coating exhibited flake decorated with nanoneedle shape. In-vitro bioactivity test conducted by immersing PSFH-CF in SBF showed that the coating could induce the nucleation and growth of bone-like apatite. Potentiodynamic polarization and electrochemical impedance spectroscopy results displayed that the multilayered coating exhibited better corrosion resistance than single layer hydroxyapatite. The excellent corrosion resistance and in-vitro bioactivity of the coating would prompt its potential application in bone tissue engineering.