Toughening and strengthening mechanisms of porous akermanite scaffolds reinforced with nano-titania

Abstract

Akermanite possesses excellent biocompatibility and biodegradability, while low fracture toughness and brittleness have limited its use in load bearing sites of bone tissue. In this work, nano-titania (nano-TiO₂) was dispersed into the ceramic-matrix to enhance the mechanical properties of porous akermanite scaffolds fabricated with selective laser sintering (SLS). The fabrication process, microstructure and mechanical and biological properties were investigated. The results showed that the nano-TiO₂ particles were dispersed both within the akermanite grains and along the grain boundaries. The grain size of akermanite was refined due to the pinning effect of the nano-TiO₂ particles on the grain boundaries. The crack deflection around the nano-TiO₂ particles was observed due to the mismatch of thermal expansion coefficients between TiO₂ and akermanite. The fracture mode changed from intergranular fracture to more and more transgranular fracture as the concentration of nano-TiO₂ increased from 0 to 5 wt%. Meanwhile, the fracture toughness, Vickers hardness, compressive strength and stiffness were significantly increased with increasing nano-TiO₂. The improvement of mechanical properties was due to the grain size refinement, the crack deflection, as well as the fracture mode transition. The bone like apatite was formed on the scaffolds in simulated body fluid (SBF). The human osteoblast-like MG-63 cells (MG-63 cells) adhered and grew well on the scaffolds. The porous akermanite scaffolds reinforced with nano-TiO₂ have considerable potential for application in bone tissue engineering.