Effect of polyethylene glycol on the electrophoretic deposition of hydroxyapatite nanoparticles in isopropanol

The suspensions of hydroxyapatite (HA) nanoparticles were prepared in isopropanol and polyethylene glycol (PEG) was used as a dispersant. The suspensions were characterized by various tests such as electrical conductivity, zeta potential, Fourier transform infrared spectroscopy (FTIR) and particle size distribution. The results showed that PEG is protonated and then adsorbed on the surface of HA nanoparticles enhancing their stability by an electrosteric stabilization mechanism. Electrophoretic deposition (EPD) was performed at different voltages (60 and 200 V) and times (15, 30, 60, 120, 240 and 360 s). EPD from the suspension with 2 g/L PEG showed the fastest kinetic due to the highest zeta potential (+32.9 mV) of HA nanoparticles in it. The wet density of deposits increased with deposition time and voltage due to the particles rearrangement within it during EPD under the influence of electro-osmotic flow. The SEM images showed that the deposit formed from the suspension with 2 g/L PEG had a finer microstructure with less agglomeration. Optical microscope images showed that PEG acted as an effective binder to prevent from deposit cracking during drying. The coating deposited from the suspension with 2 g/L PEG had the best corrosion resistance in Ringerʹs solution at 37.5 °C.