Crystalline behaviors of hydroxyapatite in the neutralized reaction with different citrate additions

Ca(OH)2 and H3PO4 were used to synthesize nano-sized hydroxyapatite. In the process of acid–base reaction, citric acid or sodium citrate was added to influence the crystallinity of hydroxyapatite. Formation of Ca-citrate complex resulted in variations of ionic concentrations and ionic activity products for solutions with different citrate additions. The degree of supersaturate was found higher for solutions with less citric acid or more sodium citrate addition. Consequently, hydroxyapatite particles with smaller size were gained. These crystalline behaviors were investigated and explained by mechanism of crystal nucleation and growth in solutions.

Nanocrystalline hydroxyapatite (HA) powders were synthesized with addition of citric acid (CiA) or trisodium citrate (NaCit). Ionic activity product and supersaturation degree of HA were varied in solutions. Higher supersaturation resulted in formation of smaller-sized crystallinite with increasing CiA addition or with decreasing NaCit addition. In comparison with that of NaCit addition, larger value of supersaturate for solutions with CiA addition resulted in formation of smaller-sized HA crystal.Figure optionsDownload as PowerPoint slide