Densification and mechanical characterization of pure and doped hydroxyapatite

Abstract

In the present study pure hydroxyapatite (HAp) and 2mol% Mg-doped, Si-doped and Zn-doped hydroxyapatite was processed and their mechanical properties were characterized. Pure and doped Hydroxyapatite powders were synthesized using the wet-precipitation method, using Calcium nitrate (Ca(NO3)2.4H2O) and Ammonium dihydrogen orthophosphate (NH4H2PO4) as precursor materials as a source for calcium (Ca²+) and phosphate ((PO4)3-) ions respectively. Pure HAp powder showed the lowest particle size of 1217 nm as indicated by DLS measurement. XRD study showed the presence of pure HAp phase in all the synthesized powders. Powders were consolidated, sintered at 1250°C for 4 hours and characterized for bulk density, indentation hardness, flexural strength and fracture toughness. Mg-Hap showed the highest bulk density of 2.96g/cc while Zn-Hap showed the highest indentation hardness, fracture toughness and bi-axial flexural strength values of 4.74GPa, 1.49MPa.m1/2 and 20.8MPa respectively. It was observed that the doped samples had a higher density, fracture toughness, bi-axial flexural strength and indentation hardness than the pure sample. The results show that doping with suitable cations can ultimately enhance the mechanical properties of hydroxyapatite ceramics.