Functionally graded silicon nitride (Si3N4) production for biomedical applications

This thesis focuses on the bio-properties and gradual production of Si3N4 material. The produced samples were differentiated in three stages from the most dense region to the less dense region. The samples, which are designed to be obtained with this structure, have been engineered at high density to meet the novel mechanical properties in the base part and low density by creating a pore in order to increase the cell penetration in the surface part. In the middle layer, it is aimed to have a smooth transition zone, so that the harmony between the two different layers is high. This FGM microstructure plays an important role as it carries both the high biocompatibility of Si3N4 and its mechanical strength on a single bulk material. Studies on Si3N4 show that it is a very important material candidate in implant applications as well as many different uses. The samples were prepared by using pure α-Si3N4 powder, Y2O3 as sintering additive and carbimide and semolina as pore-forming materials and were shaped using uniaxial press.Samples were sintered at different temperatures GPS furnace. Phase characterization by XRD analysis was performed for each layer of the grading composition. By SEM analysis, the layers forming the FGM and the inner surface of the pores in the porous designed layers were examined and the desired gradual transition between layers was observed.The bioactivity of the obtained samples was evaluated in terms of hydroxyapatite formation in SBF and the antibacterial resistance was examined by the agar well diffusion method.