Synthesis of hydroxyapatite matrix Ag and CNT particle reinforced hybrid biocomposites with improved mechanical and antibacterial properties

Hydroxyapatite is an important biomaterial for orthopaedic applications due to its high structural similarity to human bone. However, weak mechanical and antibacterial properties limit the use of hydroxyapatite compared to metallic implants such as Ti and 316L alloys for direct use in the human skeleton. To overcome these shortcomings, we have prepared hydroxyapatite matrix silver and carbon nanotube reinforced biocomposites. Silver particles have beneficial effects on biomaterials due to their effective antibacterial activity. In addition, CNT particles are known for their high strength and their ability to improve the mechanical properties of composite materials. To prepare the hydroxyapatite-based composites, the powder blends with different reinforcement types (Ag, CNT) and ratios were ground using a planetary ball mill. The biocomposite powders were then cold pressed under 500 MPa pressure to obtain green samples. The sintering process was carried out at 1200 °C for 4 h. The microstructural and structural investigations were carried out by scanning electron microscopy and X-ray diffraction, respectively. In order to better evaluate the mechanical properties of the samples, hardness measurements, compression and fracture tests were carried out. Antibacterial tests were also carried out against various micro-organisms. Both types of reinforcement were found to be effective in improving the mechanical properties. In addition, it was observed that CNT reinforcement slightly increased the antibacterial resistance, but silver-reinforced samples provided excellent antibacterial resistance.