Low-temperature Sintering and Mechanical Properties of Lithium Nibate Toughening Carbon Nano-tubes/Hydroxyapatite Biocomposites

Carbon nano-tubes (CNTs)/hydroxyapatite (HAP) biocomposites reinforced by lithium nibate (LiNbO3) were successfully prepared by hot pressing at low temperature. The phase composition and micro- structure of the composites were characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM) and Energy dispersive X-ray spectroscope (EDS). Based on in-depth analysis of mechanical properties, the toughening mechanism was discussed in detail. The results indicate that LiNbO3 addition has a great influence on mechanical properties and microstructure of the CNTs/HAp composites. The composites can be prepared at low temperature by the incorporation of LiNbO3, and LiNbO3 partially reacts with HAp to form CaNb2O6. With the rise of sintering temperature, the strength and density are improved obviously. Especially, the composite with addition of 48.5wt% LiNbO3 hot pressed at 900℃ shows excellent flexural strength and fracture toughness, of about 135 MPa and 1.71 MPa·m 1/2 , respectively. In comparison with CNTs/HAp composite, the flexural strength and fracture toughness are increased 55% and 109%, respectively. Piezoelectric energy dissipation toughening and the improvement of density are the main contributions to the increase in the mechanical properties. These new composites may be promising bone substitute materials.