Fluoro-apatite and calcium phosphate nanoparticles by flame synthesis

Calcium phosphate nanoparticles with calcium/phosphorus molar ratios ranging from 1.43 to 1.67 have been synthesized by simultaneous combustion of calcium carboxylate and tributyl-phosphate based precursors in a flame spray reactor. Fluoro-apatite and zinc or magnesium doped calcium phosphates were obtained by adding trifluoroacetic acid or corresponding carboxylates into the fuel. Nanoparticle morphology and the structure of sintered ceramics were studied using transmission and scanning electron microscopy. Thermal evolution of calcium phosphate phases was investigated by powder X-ray diffraction, Fourier transform infrared spectroscopy, and thermal analysis. A molar ratio of Ca/P < 1.5 in the precursor promoted the formation of dicalcium pyrophosphate (Ca2P2O7). Phase pure beta-tricalcium phosphate was obtained with a precursor Ca/P ratio of 1.52 after subsequent calcination at 900 degreesC. The regular, open structure with interconnecting micropores and the facile substitution of both anions and cations suggests possible application as a biomaterial.