Variation of Vickers microhardness and compression strength of the bioceramics based on hydroxyapatite by adding the multi-walled carbon nanotubes

Calcium phosphate ceramics for medical applications with additives of multi-walled carbon nanotubes were synthesized at a temperature of 1100 °C in the argon atmosphere. The concentration of nanotubes ranged from 0.05 to 0.5 wt.%. The morphology and structure of the powder of multi-walled carbon nanotubes and calcium phosphate ceramics have been characterized by the electron microscope. The most part of the initial nanotubes have distributions of outer diameter 10–25 nm. The multi-walled carbon nanotubes are located in the intergranular space, change their shape and aspect ratio. Diffraction patterns of ceramics show that all samples have apatite structure and any distinct reflections except those of hydroxyapatite are detected. The partial carbonization of ceramics is indicated by the results of FT-IR studies. With an increase of the amount of nanotubes in composite ceramics, the intensity of the carbonate stretching band increases, which may be due to partial oxidation of the nanotubes and as a result leads to more intensive carbonization of the apatite phase. It was found that the mechanical properties of ceramics (compression strength and Vickers microhardness) were improved with the increasing of the amount of nanotubes.