Thermal Treatment of Flame-Synthesized Amorphous Tricalcium Phosphate Nanoparticles.

Flame-spray synthesis was used to produce nanoparticulate X-ray amorphous tricalcium phosphate. Upon heating, the material crystallized at temperatures between 525° and 600°C, yielding α-tricalcium phosphate (TCP) with minor amounts of β-TCP and hydroxyapatite (HA). Further heating induced a gradual transformation of α- to β-TCP accompanied by crystallite growth and particle fusion. α-TCP was completely transformed into β-TCP at 950°C. The high-temperature polymorph α′-TCP was not observed. In transmission electron microscopy and selected area electron diffraction analyses, the raw material appeared completely amorphous and samples heated previously to 600° and 700°C comprised single-crystalline particles of α-, β-TCP, and HA. The results of this study demonstrate that nanoparticulate α-TCP can be obtained from flame-spray-synthesized amorphous nanoparticles at temperatures where sintering effects such as particle growth and fusion are moderate, if not negligible. [ABSTRACT FROM AUTHOR]