Deposition, nanostructure and phase composition of suspension plasma-sprayed hydroxyapatite coatings

Nanostructured hydroxyapatite (HA) coatings were successfully deposited on stainless steel substrates by suspension plasma spray (SPS) method. The suspension was prepared by a wet chemical method using Ca(NO3)(2) and (NH4)(2)HPO4 as source materials. The TEM morphologies show that these HA particles are needle-like nanowires. The effect of hydrogen flow rate of plasma forming gas on the coating properties has been intensively studied. FE-SEM images confirm that coatings are nanostructured. X-ray diffraction pattern shows that as-sprayed coatings are HA phases and the crystal size is estimated to be less than twenty nanometers when low hydrogen flow rate is used. When high hydrogen flow rate is utilized, secondary phases appear in the as-sprayed HA coatings and the crystal size increases to dozens of nanometers. Fourier transform infrared spectroscopy and MicroRaman spectroscopy indicate the significant presence of OH- and CO32- ions in the coatings. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.