Spark Plasma Sintered Hydroxyapatite/Multiwalled Carbon Nanotube Composites With Preferred Crystal Orientation†

Hydroxyapatite (HA) and its nanocomposites reinforced with low loading levels of multiwalled carbon nanotubes (MWNTs) are prepared by spark plasma sintering process. The structure, morphology, and hardness of sintered HA and MWNT/HA nanocomposites are characterized by means of X-ray diffraction (XRD), scanning electron microscopy and nanoindentation techniques. XRD results show that the orientation of crystallographic planes of sintered HA are highly related to the applied pressure direction. The perpendicular section of sintered MWNT/HA nanocomposites shows predominantly oriented HA a-and b-planes while the parallel section displays a dominant c-plane orientation. The hardness of MWNT/HA nanocomposites improves considerably with increasing MWNT content.