Electrophoretic deposition of nanocrystalline hydroxyapatite on Ti6Al4V/TiO2 substrate

• Published in: Journal of Coatings Technology and Research 2013-03, Vol.10 (2), p.263-275
• Main Authors: Jain, Prateek, Mandal, Tapendu, Prakash, Prem, Garg, Ashish, Balani, Kantesh
• Format: Article
• Language: English
• Subjects: Chemistry and Materials Science; Corrosion and Coatings; Industrial Chemistry/Chemical Engineering; Materials Science; Polymer Sciences; Surfaces and Interfaces; Thin Films; Tribology
• ISSN: 1547-0091; 1935-3804
• DOI: 10.1007/s11998-012-9438-2

Hydroxyapatite is a bioactive material that is the main inorganic constituent of human hard tissue (Ca/P ratio of 1.67) whose coatings provide requisite surface bioactivity to the bone implants. In the current work, the characteristics of nanocrystalline hydroxyapatite (HA) coatings, electrophoretically deposited on Ti6Al4V substrate, have been investigated. To enhance the coating’s compatibility, a 0.75 μm thick TiO 2 layer was thermally grown as a diffusion barrier prior to electrophoretic deposition of HA. Subsequently, HA was electrophoretically deposited (EPD) at different deposition voltages (100–250 V) while keeping the deposition time as 10 s. Both anodic oxidation during EPD for 10 s and thermal oxidation during sintering at 1000°C for 2 h resulted in the growth of a TiO 2 layer thickness of more than 25 μm. Enhancement of voltage also has shown significant influence on the mechanism of the evolution of biphasic microstructures, attributed to the simultaneous growth of TiO 2 and HA phases. Optimized distribution of HA and TiO 2 phases was evidenced at 200 V, with explicit HA retention as observed via transmission electron microscopy. An empirical relationship is developed to relate the voltage with the suppression of cracking in the deposited coatings.