La and F co-substituted hydroxyapatite bioactive coating reinforced by SiC nanowire/ZrO₂ hybrid materials for carbon/carbon composites

La and F co-substituted hydroxyapatite (LFH) bioactive coatings reinforced by SiC nanowire/ZrO₂ (SZ) hybrid materials were applied on carbon/carbon composites using a combination method of chemical vapor deposition, slurry process, electrochemical deposition and immersion process. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscope and X-ray photoelectron spectroscopy (XPS) were adopted to investigate the morphology, microstructure and composition of the coating. The adhesion strength of the coating was investigated by tensile test and the in-vitro bioactivity of the coating was studied using simulated body fluid (SBF) immersion test. The results showed that SZ hybrid reinforcement exhibited a porous and latticed structure, which favored the infiltration of LFH crystals and the integration between SZ and LFH. LFH showed a flake-like shape with a thickness of 20-60 nm and a length of 1-3 μm. The average adhesion strengths of unreinforced and SZ reinforced LFH coating were 2.97±0.32 MPa and 12.37±0.84 MPa, respectively. The in-vitro bioactivity test confirmed that the SZ reinforced LFH coating could induce the nucleation and growth of bone-like apatite on its surface in SBF. It was suggested that the SZ reinforced LFH coating might be an effective method to improve the surface bioactivity of carbon/carbon composites with excellent adhesion strength.