Synthesis and characterization of Si-substituted hydroxyapatite bioactive coating for SiC-coated carbon/carbon composites

A silicon-substituted hydroxyapatite (Si-HA) coating for SiC-coated carbon/carbon composites has been prepared by pack cementation and electrochemical deposition. The morphology, microstructure and in-vitro bioactivity of the Si-HA/SiC double-layer coatings were investigated. Results showed that the SiC inner-layer exhibited high crystallinity. The Si-HA outer-layer had a smaller crystal size than pure hydroxyapatite (HA). Simulated body fluid (SBF) immersion tests showed that the Si-HA coating was uniformly covered by a layer of apatite after 7 days of immersion, while the apatite layer formed on the HA coating was inhomogeneous. This work demonstrates that the Si-HA coating may have better bioactivity than a HA coating and shows promise for the potential application as bioactive coating.