Tailored mechanical properties of silicon nitride–hydroxyapatite composite scaffolds for biomedical applications

Abstract Silicon nitride (Si ₃ N ₄ )–hydroxyapatite (HA) composite scaffolds for bone replacement were developed via pressure infiltration of HA into a porous Si ₃ N ₄ matrix. The effect of replication processing parameters (SiO ₂ content, number of infiltrations, and calcination temperature) on the structure and mechanical properties of the porous Si ₃ N ₄ matrix was investigated and compared to human trabecular bone. All fabricated Si ₃ N ₄ matrices exhibited interconnected porosity comparable to trabecular bone. A matrix processed with double infiltration with 15 wt.% SiO ₂ suspension, followed by calcination at 1100°C, demonstrated the highest compressive strength. Subsequent pressure infiltration with HA significantly enhanced both the compressive (∼ twofold) and tensile strength (> quadruple) of this matrix, yielding a composite scaffold with a compressive strength similar to that of human trabecular bone, while maintaining comparable microporosity.