Nanocomposites and nanomaterials

Influence of the additives of multi-walled carbon nanotubes to the porosity of hydroxyapatite composite 

M.S. Barabashko1, R.M. Basnukaeva1, M.V.Tkachenko2 

1 B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, 47 Nauky Ave., Kharkiv 61103, Ukraine
E-mail: msbarabashko@gmail.com 
2 V.N. Karazin Kharkiv National University, 4 Maidan Svobody, Kharkiv, 61077, Ukraine

Hydroxyapatite (HA) powder was synthesized by the reaction between calcium carbonate and orthophosphoric acid. Calcination of the obtained HA powder was carried out at 900C for 1 h. The cylindrical compacts were obtained from calcined powder under a pressure 120 MPa. Composite ceramics based on hydroxyapatite (HA) with additives of multi-walled carbon nanotubes (MWCNTs) have been sintered in the Ar atmosphere. The concentration of nanotubes was varied in the range 0 - 0.5 wt%. HA is a bioactive matrix, while MWCNTs additives can improve the mechanical properties of ceramics. In particular, the additives of MWCNTs lead to the unique electrical, thermal, and mechanical properties of composite materials. 
X-ray, IR, and TEM have been studied. In addition, the increase of the density and decrease of the porosity have been observed. The obtained results are discussed. It was found that HA ceramics has higher macrostresses than in the case of HA ceramics with the additives of MWCNTs. HA ceramics have low thermal diffusivity and the temperature gradients occur during heterogeneous heating/cooling of different parts of ceramics at sintering. The additives of MWCNTs allow to increase the thermal diffusivity and reduce internal residual macrostresses in the HA-MWCNTs ceramics. 

Acknowledgments: We are grateful for National Research Foundation of Ukraine (Grant No.197/02.2020).