A Novel Bio-Nanocomposites Composed of Hydroxyapatite Reinforced with TiO2 Electrospun Nanofiber Consolidated Using High-Frequency Induction Heating

Abstract

Titanium dioxide (TiO2) nanofibers prepared by the electrospinning technique have been used as reinforcement to improve the fracture toughness of hydroxyapatite (HAp). The required TiO2 nanofibers with diameters of 50–400 nm were first prepared by the calcining and presintering of as-prepared electrospun nanofibers of polyvinyl acetate (PVac)/titania composite at different temperatures. The composite consisting of HAp and 5 wt% of electrospun TiO2 nanofibers was then sintered at 1050° C by the high-frequency induction heat-sintering technique and its mechanical properties are evaluated by three-point bending tests, indentation tests, and a compression test. The results indicated that the morphology and crystalline phase of TiO2 nanofibers were strongly influenced by the calcination temperature. Additionally, the scanning electron microscopic results showed that the nanofibers calcined at 600°C are a porous structure due to the low densification. There was a significant change of microstructure by increasing the calcination temperature to 800°C. The nanofibers appeared with a dense microstructure due to the high-temperature calcination. A number of large size particles or particle aggregates connected by a small neck were found after the nanofibers were calcined at 1000°C. The sintering behaviors, toughness, and hardness of the resulting composites were significantly affected by the calcination temperature of the included TiO2 nanofibers. The bending and compressive strength values of HAp/5 wt% TiO2 sintered compacts were 119 and 120 Mpa, respectively, in the case of the TiO2 nanofiber calcined at 800°C, while the strength decreased with the decreasing or by increasing calcination temperature higher than 800°C.