Improved dispersion of SiC whisker in nano hydroxyapatite and effect of atmospheres on sintering of the SiC whisker reinforced nano hydroxyapatite composites

Abstract

In order to improve the mechanical properties of nano hydroxyapatite (HA), silicon carbide whisker (SiCw) with excellent mechanical and biological properties was used as the reinforcement for SiC whisker reinforced nano hydroxyapatite (SiCw/HA) composites. Hydrothermal synthesis method was adopted to prepare the uniformly dispersed SiCw and HA composite powders, and SiCw/HA composites were fabricated by pressureless sintering. The interfacial bonding state and mechanical properties of SiCw/HA composites in different sintering atmospheres (air and N2) were systematically investigated. The results show that the uniformity of the composite powders decreases with the increase of SiCw content, and the cross-section of SiCw/HA composites gradually changes from glossy and smooth to rough and undulate. When the content of SiCw is 15 wt%, the maximum bending strength and fracture toughness of the composites sintered in air atmosphere (HAW15) are 40.85 MPa and 1.82 MPa·m1/2 respectively, which are higher than those of pure HA. Compared with those of the SiCw/HA composites sintered in N2 atmosphere, the bending strength and fracture toughness of the HAW15 composites are increased by 154.2% and 10.3%, respectively. Moreover, Simulated body fluid (SBF) and in vitro cell behavior tests indicate that the SiCw/HA composites still have excellent bioactivity. The possible strengthening and toughening mechanisms of SiCw/HA composites are that the dispersion of SiCw in HA matrix is improved by hydrothermal process, and the interfacial bonding property is enhanced because of the reaction fusion on interface of SiCw/HA composites during sintering in air atmosphere. The adoption of hydrothermal process improves the dispersion uniformity of SiCw in HA matrix. When sintering in air atmosphere, the interfacial bonding property of SiCw/HA composite is enhanced via the reaction fusion (SiO2 is formed by the oxidation of SiCw). Both of them lead to the increase of strength and toughness of the composites. This study would provide additional insights into the feasibility of SiCw/HA composites as load-bearing implant materials in orthopedic applications.