Ethanol-based sol-gel synthesis of nano-crystalline hydroxyapatite with different calcium phosphorus ratios (Ca/P)

One of the easy ways to prepare nanocrystalline hydroxyapatite (nano-HAp) is the sol-gel method that due to its unique advantages compared to conventional methods, has raised research interest among scientists. The purpose of this study was to investigate the properties of nano-HAp powders which were synthesized by ethanol-based sol-gel method with stoichiometric ratio of Ca/P = 1.67 and comparing it with closer ratios of 1.5 and 1.6. To do so, we used the aqueous solution of phosphorus pentoxide (p(2)0(5), MERCK) and four-watered calcium nitrate (Ca (NO3)(2).4H(2)O, MERCK) in ethanol. The resulted nano-powders and sintered pellets made of it were analysed and compared with X-ray diffraction analysis (XRD). Also, the sintered pellets' bioactivity in simulated body fluid (SBF) solution was examined by SEM. In powders which were calcined at the temperature of 600 degrees C, the most amorphous phase (49%) in comparison to Ca/P = 1.5 was observed. After sintering, the main phase of 1.67 ratio was hydroxyapatite (HAp) and the main phase of 1.5 ration was beta-TCP, although in 1.6 ration a composite of HAp and beta-TCP was observed. According to the results, sol-gel method for producing nanocrystalline HAp was an appropriate method; in addition, compared with the different ratios of Ca/P, the stoichiometric nanocrystalline may have better bioactivity.