Rapidly formation of the highly bioactive surface with hydroxyapatite crystals on the titania micro arc oxidation coating by microwave hydrothermal treatment

Abstract

In order to enhance the bioactivity of the microarc oxidation (MAO) coating on titanium (Ti), a rapid modification technique of microwave hydrothermal (MH) treatment was used to form the dense, uniform and abundant hydroxyapatite (HA) crystals on the MAO coating surface. During the MH treatment, the calcium (Ca) and phosphorus (P) elements were migrated from the inner layer to the outer layer, creating the Ca2+ and PO43− ions, then reacted with the OH− ions in the NaOH aqueous, thus forming the HA crystals on the MAO coating surface within several minutes. With the increasing of the MH treatment time (15 and 60 min), the amounts of Ca and P elements in the MAO coating were greatly reduced according to the energy dispersive X-ray spectroscopy (EDS) results. Meanwhile, lots of Na0.23TiO2 nanoflakes were formed due to the chemical reaction between TiO2 and NaOH. The MAO coating after the MH treatment for 10 min showed a higher surface hardness and Young's modulus on the modified coating surface due to the formation of the dense and abundant HA crystals. Moreover, the MH treated MAO coatings showed rough and porous surfaces, good surface wettability, high surface energy and surface potential. The apatite formation ability of the MH treated MAO coating was significantly improved resulting from the formation of the abundant HA crystals.