Effects of titanium and carbon nanotubes on nano/micromechanical properties of HA/TNT/CNT nanocomposites

Abstract

In this study, hydroxyapatite/titanium nanotube/carbon nanotube (HA/TNT/CNT) nanocomposites with different CNT contents were fabricated using a combination of hydrothermal and sol–gel methods. The nanocomposite powders were pressed at 350 MPa using the cold isostatic pressing technique and sintered at 1050 °C in a tube furnace in the presence of Ar gas. The nano/micromechanical properties, biocompatibility, and tribological characteristics of HA-based composites (with versatile mass ratios of CNT: 1.0, 1.5, and 2.0 wt%) were investigated. According to hardness-test results, the HA/TNT/CNT (2.0 wt% CNTs) composite exhibited the highest surface hardness (235.9 HV) among the samples. Wear-resistance tests were performed under different normal loadings. HA/TNT/CNT with higher CNT content exhibited a lower wear rate than the other samples. Nanoindentation tests were performed, and the nanohardness and elastic modulus of the HA were 62.41 and 1.821 GPa, respectively. These values were increased to approximately 98.7 and 5.3 GPa, respectively, for HA/TNT/CNT-2.0 (after the addition of TNTs and CNTs). The inclusion of 2.0 wt% CNTs in the HA/TNT composite reduced the wear debris volume by ∼ 66% owing to the enhanced modulus of elasticity and hardness. Moreover, in-vitro biocompatibility tests revealed that HA/TNT/CNT-2.0 had no cytotoxicity.