Reactivity of calcium phosphatenanoparticles prepared by flame spray synthesis as precursors for calcium phosphate cements

Abstract

Flame-spray synthesis was used to produce calcium phosphate nanoparticles with a Ca/P molar ratio in the range of 0.5 to 2.0. The use of these powders as raw material for calcium phosphate cements was then assessed. Various characterization techniques revealed that prepared particles consisted of white spheres, had a diameter in the range of 20–30 nm, and formed loose agglomerates. The composition varied from acidic to basic calcium phosphates when the Ca/P molar ratio was increased from 0.5 to 2.0. At the lowest ratio, monocalcium phosphate monohydrate (MCPM) and dicalcium phosphate dihydrate (DCPD) were detected, whereas hydroxyapatite was found at the highest Ca/P molar ratio. All but one of the powders (Ca/P molar ratio = 2.0) reacted with water to form a more crystalline phase. The reaction was highly exothermic and proceeded within a few hours. The reaction product ranged from MCPM/DCPD to hydroxyapatite depending on the initial Ca/P molar ratio. These results suggest that new calcium phosphate cements can be attained using these powders produced by flame-spray synthesis.