Functionally graded bioactive coatings of hydroxyapatite/titanium oxide composite system

Abstract

Hydroxyapatite powder (P81B, HA, Plasma Biotal, UK) was mixed with titanium oxide (TiO2) in different weight percentages for producing functionally graded bioactive coatings. Composite coatings were made on Ti6Al4V metal substrate. A functionally graded coating was obtained by coating titanium oxide (TiO2) powders of known particle size as the first layer, which was sintered at 900 °C for a few minutes. Coating of subsequent layers of HA-TiO2 composites of different weight ratios (75% TiO2 and 25% HA, 50% TiO2 and 50% HA, 25% TiO2 and 75% HA, and 100% HA) were performed in sequence and these layers were sintered again at 900 °C for a few minutes so as to ensure a good adhesion between layers. The coatings were subsequently subjected to various characterization such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier infra-red spectroscopy (FTIR) and hardness studies. The XRD results confirmed the presence of the corresponding components in HA composites. SEM micrographs showed the surface morphology of the functionally graded layers, and the presence of elements was also identified by EDX analysis which confirms the versatility of the coating technique performed at low temperature. Nano-indentation studies revealed that HA-TiO2-Ti functionally graded coating yielded 15.1 and 0.405 GPa as the hardness and modulus values, respectively. © 2002 Elsevier Science B.V. All rights reserved.