ABSTRACT
The starting sols were prepared by ultrasonic mixing of concentrated solutions of calcium nitrate (5M), Ca(OH)2 slurry or calcium acetate (1.7M) with 85% H3PO4 followed by emulsification in dehydrated 2-ethyl-l-hexanol. Drops of emulsion were solidified by extraction of water with this solvent. The process was carried out continuously. When starting from acetate sols spherical powders were obtained. Irregularly shaped powders were obtained from nitrate sols and Ca(OH)2 slurry. In all cases, particle diameters were below 100 microns. The separated gel particles were calcined to calcium phosphates with molar ratio Ca/P from 0.8 to 2.8. This process was studied using differential thermal analysis (DTA), thermogravimetry (TG), x-ray diffraction analysis (XRD) and infrared spectrometry (IR). Hydroxyapatite was obtained from acetate Ca-P gels. However for Ca/P molar ratios higher than 2 the product contained CaO or even CaCO3.
