Functionalized silicon nitride for bio-applications

Silicon nitride is an established biomaterial already implanted in human body. Further improvement in silicon nitride performances could be achieved by its functionalization. Compositing silicon nitride with an electroconductive phase such as titanium nitride allows to reach outstanding mechanical behavior and the possibility of manufacturing complex parts by electro discharge machining from simple shaped components. This machining technique is cost-effective and opens the possibility to customize the large bearing surfaces with complex topographies through CAD-CAM rendering. Moreover the near net shaping through wet forming techniques, opens new opportunities for the production of complex architectures in which the specifically designed porosity is no more a defect but a functional property to exploit for bone substitution. The route used to produce highly porous silicon nitride (over 70%) was the direct foaming and casting of aqueous suspensions by exploiting the foaming property of ovalbumin and its ability to thicken after heating, the so-called clot forming. Specific surface areas up to 70 m2/g and compressive strength ranging 20-30 MPa were obtained.