Microhardness and microstructural properties of a mixture of hydroxyapatite and β-tricalcium phosphate

Calcium phosphate ceramics have been studied as promising materials for biomaterial applications owing to their excellent biocompatibility and osteoconductivity. Herein, we investigated the influence of different mass ratios of hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) in a calcium phosphate mixture (CPM) on the microhardness and microstructural properties of a series of xHA-(100-x)β-TCP (x = 0, 30, 50, 70, 90, and 100) mixture samples. The chemical compositions and structural properties of the CPM samples were characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The porosity of the HA/β-TCP composites decreased with increasing β-TCP content and reached a minimum porosity when the mass ratio of HA/β-TCP is 70/30, and then increased with increasing β-TCP content again. The surface microhardness of the CPM composites was measured and found to be inversely proportional to their porosities. Therefore, the CPM of HA/β-TCP with a mass ratio of 70/30 exhibited a maximum surface microhardness of 86.02 MPa.