Electrophoretic deposition of hydroxyapatite fiber reinforced hydroxyapatite matrix nanocomposite coatings

•EPD of Fiber (F-HA)/Sphere (S-HA) hydroxyapatite composite coatings were performed.•S-HA was bonded to F-HA particles in TEA-containing suspensions.•F-HA particles efficiently reinforced the microstructure of composite coatings.•Coarse pores were formed by stacking of long F-HA particles in deposit during EPD.•Finer S-HA particles efficiently filled these coarse pores during EPD.

Two-component suspensions of hydroxyapatite nanoparticles with spherical (S-HA) and fiber (F-HA) morphologies were prepared in isopropanol using triethanolamine (TEA) as the dispersant. In-situ kinetics of deposition and current density were recorded during EPD at 60 V from suspensions with different wt% of F-HA and TEA. f factor decreased against TEA concentration in all suspensions except the one-component suspension of F-HA particles. The detachment of particles from single component F-HA deposits did not occur during EPD due to the mechanical interlocking of F-HA particles in their microstructure. F-HA particles reinforced the coatings and prevented from their cracking during drying by bridging mechanism. S-HA particles infiltrated and filled the pores formed by stacking of the F-HA particles in deposit. S-HA particles were also grafted to F-HA particles in TEA-containing suspensions via hydrogen bonding between TEA molecules adsorbed on the particles. The coating deposited from the suspension with 75 wt% of F-HA particles had the best corrosion resistance in SBF solution at 37.5 °C.