Sol–gel synthesis of nanostructured hydroxyapatite powder in presence of polyethylene glycol

A study on the morphological changes of nanostructured hydroxyapatite in presence of polyethylene glycol synthesized by sol–gel technique is presented. Equimolar solutions of Ca(NO3)2·4H2O and (NH4)2HPO4 dissolved in ethanol were used in the synthesis at 85 °C. Polyethylene glycol is added as an organic modifier. The product was sintered at 400, 750 and 1100 °C. The XRD and FTIR results indicated the presence of amorphous hydroxyapatite in as dried gel precursor and single phase HAP was obtained after heat treatment at 1100 °C at 4 h. SEM images of the precursor appear agglomerated leaving sub micrometric pores between them and the small particles seen embedded in each agglomerated cluster with an average diameter of 50–70 nm. At high temperatures the more flexible polyethylene glycol molecules induced the orientation growth which leads to the formation of HAP platelets.