A study of the process and kinetics of electrochemical deposition and the hydrothermal synthesis of hydroxyapatite coatings

Hydroxyapatite (HAp) coatings were prepared using electrochemical depositio n and post-hydrothermal synthesis. The composition and morphology of coatin gs at each processing step was studied through the application of scanning electron microscopy (SEM), X-ray diffraction (XRD) and infra-red spectrosco py (IR). The mechanism and kinetics of hydrothermal synthesis were consider ed in particular, and the influnce of the temperature and time on the HAp f ormation rate was also investigated. The results show that the electrochemi cal deposition coatings are composed of CaHPO(4)2H(2)O crystals which are c onverted into needle-like HAp crystals after post-hydrothermal treatment. T he HAp content of the coatings increases with the treatment temperature and time. The synthesis rate also increases with the pH value of the water. Th e formation of HAp coatings is considered to be a combination of several re actions. An Arrhenius relationship was found between the HAp formation rate and the temperature, and an apparent activation energy of 94.4 KJ/mol was obtained by calculation. (C) 2000 Kluwer Academic Publishers.