Synthesis of nano-sized biphasic calcium phosphate ceramics with spherical shape by flame spray pyrolysis.

Nanometer size biphasic calcium phosphate (BCP) powders with various Ca/P molar ratios satisfied with appropriate phase ratios of HA/beta-TCP were prepared by high temperature flame spray pyrolysis process. The BCP powders had spherical shapes and narrow size distributions irrespective of the ratios of Ca/P. The mean size of the BCP powders measured from the TEM image was 38 nm. The composition ratio of Ca/P was controlled from 1.500 to 1.723 in the spray solution, and required phase ratios of HA/TCP are controlled systematically. The calcium dissolution of the pellets obtained from the BCP powders directly prepared by flame spray pyrolysis in buffer solution increased with the decrease of Ca/P ratios except with the Ca/P ratio of 1.713. The pellet surface with Ca/P ratio of 1.500, which consisted of beta-TCP, was eroded dramatically for 7 days. On the other hand, the pellet surface with Ca/P ratio of 1.667 was stable and did not disintegrate after immersion in Tris-HCl buffer solution based on the SEM observation.