Fabrication and characterization of needle-like nano-HA and HA/MWNT composites.

Hydroxyapatite (HA) ceramic has been used in tissue engineering and orthopedics for its good biocompatibility and osteoconductivity. However, its clinical applications are usually limited by the low strength and brittleness. The objective of this research was to develop a new kind of HA composites in which multi-wall carbon nanotubes (MWNTs) were introduced to the HA ceramic matrix to improve the mechanical properties of the resulting composites. A simple chemical wet method was applied to synthesize the HA ceramic particles with the aid of surfactant and ultrasonication technique at normal atmospheric pressure. The morphology and microstructure of the synthesized HA were characterized by XRD and TEM as a function of treatment time. The results showed that the synthesized HA particles are needle-like with a length of 80-160 nm along the (211) direction and an aspect ratio of 5-15. MWNTs were treated with a mixture of nitric acid and sulfuric acid. The HA/MWNT composites were prepared by solution blending. The composites were sintered using a hot-press method. The mechanical properties of the HA/MWNT composites with different volume percentages of MWNTs were examined. The fracture toughness and flexural strength were improved by 50% and 28% separately when the volume percentage of MWNTs reached 7%.