Design and fabrication of porous functionally graded akermanite-based composites for bone tissue engineering applications

Abstract

In this study, a four-layer functionally graded composite (FGC) based on akermanite was fabricated by incorporating titanium silicon carbide, silicon nitride, zinc oxide, and niobium carbide reinforcements at different volume fractions using a controlled compositional gradient and a space-holder technique to produce porous structures. The novelty of this work lies in developing a multifunctional akermanite-based graded architecture that combines different ceramic reinforcements to achieve synergistic improvements in tribo-mechanical properties, degradation behavior, and bioactivity. The physical and tribo-mechanical properties were evaluated. Additionally, the bioactivity of all prepared FGC layers was evaluated using simulated body fluid (SBF). An investigation was also performed using field-emission scanning electron microscopy (FESEM) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). FESEM demonstrated good bioactivity across all sample layers, driven by the optimal formulation, porous structures, and surface roughness that promote apatite formation. The bioactivity of the prepared samples was confirmed by significant consumption of Ca²⁺ and PO₄³⁻ ions from the SBF solution. The bulk density of all FGC layers produced was low, ranging from 2.38 to 2.50 g/cm³. The microhardness of the FGC sample layers ranges from 3.189 to 4.618 GPa, consistent with the FGC sample's microhardness, providing a strong indication of the quality of preparation and a good hardness distribution with minimal mixing. The results demonstrated the impact of surface roughness and inherent hardness of the integrated ceramic phases on the frictional performance of the produced composites. For example, the friction coefficients of the fabricated layers decreased by 3.42%, 8.42%, and 11.31%, respectively, due to these factors, compared to the layer free of ceramic reinforcements. Based on the above results, the developed FGC demonstrated promising characteristics for bone tissue engineering applications.