FHA coating for C/C composites prepared by sonoelectrodeposition and treatment of NaF

Fluorine-containing hydroxyapatite (FHA) coatings on the surface of carbon/carbon composites were prepared using the methods of sonoelectrodeposition and treatment of NaF. The effects of treatment time on morphology, structure and composition of the as-received coating were investigated by SEM, EDAX, FTIR XPS and XRD. The results show that NaF promoted the change tricalcium phosphate to fluoridated hydroxyapatite with increasing of crystallization degree of the coating. After the treatment of NaF, the composition of coating were a mixture of HA and F-rich apatite (FA) at different ratio, and (112) and (300) peak shifted to a higher angle than that of pure HA. With the treatment time increasing, the HA content in the coating decreased, while F-rich apatite (or FA) increased. The coatings are both plate-like crystals before and after treatment, however, the size of the crystals change after treatment. When treatment time reached 48 h, the coating was dense, and fluorine content of the coating was 5.85 wt%. The bonding strength increased slightly after the treatment of NaF, the bonding strength could reach 4.08 MPa.