Effect of triethanolamine on the electrophoretic deposition of hydroxyapatite nanoparticles in isopropanol

Suspensions of hydroxyapatite (HA) nanoparticles were prepared in isopropanol and triethanolamine (TEA) was used as the dispersant. It was found that H+TEA species generated by proton capturing from isopropanol are chemically adsorbed on HA nanoparticles via strong hydrogen bonding, enhancing their zeta potential and hence colloidal stability. Electrophoretic deposition was performed at 60 V for various durations. It was found that sticking parameter (f factor) decreases with TEA concentration due to the increase in the potential (electrical+chemical) difference at the interface of deposit and suspension. The wet density of deposits increased with the zeta potential of particles as well as deposition time, due to the time dependent rearrangement of particles within the deposit caused by electro-osmotic flow which is stronger when the zeta potential is higher. It was found that the coating deposited from the suspension with 4 mL/L TEA had the best corrosion resistance in Ringerʹs solution at 37.5 °C due to its fine, homogeneous and crack-free microstructure acting as a good barrier against the corrosive medium.