Effect of calcium fluoride on mechanical behavior and sinterability of nano-hydroxyapatite and titania composites

Composites of nano-hydroxyapatite (HA) – titania (TiO2) with or without calcium fluoride (CaF2) were synthesized and sintered at 900 °C, 1100 °C, and 1300 °C. The composites were studied to assess the effect of CaF2 addition on the sinterability, structure, functional groups, morphology and mechanical behavior of the material. The resultant composites were characterized by XRD, ATR-FTIR, SEM and microhardness measurement, respectively. It was seen that the addition of CaF2 into HA–TiO2 composites enhanced the densification via reducing the porosity of the composites. The XRD results showed that as the amount of TiO2 in the composites was increased, transformation of HA into tricalcium phosphate (TCP) was favored due to the formation of calcium titanate (CaTiO3). On the other hand, the addition of CaF2 into the composites led to the shrinkage of unit cell volume of HA due to the substitution of F− ions into HA and suppressed the decomposition of HA in these composites. Moreover, the addition of CaF2 also improved the microhardness of the composites.