Coating of hydroxyapatite films on metal substrates by seeded hydrothermal deposition

Hydroxyapatite (HAP) was successfully coated on various metal substrates by a novel seeded hydrothermal deposition method. A nanoscale HAP seed layer was first formed by a short electrochemical synthesis. The seed layer promotes HAP crystal growth onto the surface during a subsequent hydrothermal crystallization step. The surface morphology and microstructure of the HAP coatings can be regulated by varying the reaction temperature, solution pH, calcium-to-phosphorus molar ratio in the starting solution, and hydrothermal deposition time. The new method has advantages over many other reported HAP deposition techniques in that it produces highly crystalline, crack-free, adherent films of uniform thickness. In all the films, the HAP crystals are preferentially oriented with the c-axis normal to the substrate. The as-developed HAP coatings are attractive for applications in the area of bioactive surface modification of metallic implants where the microstructure of the film is advantageous for promoting bone growth.

Research highlights
► New hydroxyapatite coating method of hydrothermal growth onto seeded substrates.
► Uniform and fully crystallized hydroxyapatite coatings were formed on metal surfaces.
► Crystals in the coating were oriented with the c-axis normal to the substrate.
► Coating thickness and morphology were adjustable.