Surface Characteristics of RF Magnetron Sputtered Calcium Phosphate Coatings at Different Heat Treatments
RF magnetron sputtering was used to produce calcium phosphate coatings on titanium substrates. The as-sputtered amorphous calcium phosphate (CaP) coatings were subjected to a rapid heating with infrared irradiation and subsequent heating in an autoclave. XRD analyses showed that infrared radiation of the amorphous coatings changed respectively into a crystalline apatite- and a β-pyrophosphate structure. Heating in the autoclave showed for the amorphous CaP coating at 80°C for 2 days and 8 hours at 140°C no change in structure and the formation of a crystalline apatite structure respectively. The amorphous pyrophosphate(Pyro) coating altered during the autoclave treatment for 2days at 80°C into a monetite phase, while at 140°C an apatite structure was formed. SEM analyses demonstrated that after the different heat-treatments several coating morphologies were obtained. Infrared radiation had no effect on the coating morphology. The autoclave-treated coatings showed the formation of a calcium phosphate precipitate. CaP and Pyro coatings induced a morphologically different precipitate. On the CaP coating, spherocrystallites crystals were formed and the Pyro coatings showed the formation of needle like crystals. EDS analyses indicated for the autoclave heat treated Pyro coating an increase of the Ca/P ratio from 0.8 to 1.7.
Panjian Li, Kai Zhang and Clifford W. Colwell, Jr.
Y. Yonggang et al., "Surface Characteristics of RF Magnetron Sputtered Calcium Phosphate Coatings at Different Heat Treatments ", Key Engineering Materials, Vols. 284-286, pp. 235-238, 2005