Pressureless sintering and mechanical properties of hydroxyapatite/functionalized multi-walled carbon nanotube composite

This work aims to study the optimum sintering conditions of hydroxyapatite/functionalized multi-walled carbon nanotube (HA/f-MWCNT) composite with improved mechanical properties for bone implant applications using a pressureless sintering technique. The carboxyl functional group (-COOH) introduced by the acid treatment on the MWCNT surface by which HA molecules are grafted onto the surface of functionalized MWCNT with strong interfacial bonding. The composite exhibits a lower hemolytic rate of 1.27%. The flexible nature of f-MWCNT makes them bend and attached to the HA grains, indicates that f-MWCNT bear significant stress by sharing a portion of the load and it leads to improve their mechanical properties. The maximum Vickers hardness of 3.6 GPa is obtained for the HA/f-MWCNT composite sintered at 1100 °C, whereas the highest compressive strength of 481.7 MPa and fracture toughness of 2.38 MPa.m^1/2 achieved after sintering at 1150 °C. This study demonstrated that HA/f-MWCNT composite create suitable structures by vacuum pressureless sintering technique to satisfy the mechanical requirements for bone tissues.