Structure and Bulk Properties of Silicon Nitride

What is it about?

Silicon nitride has been developed over many decades of intensive research. This has resulted in a ceramic with unique properties that arise through the main processing route for the material. This involves liquid-phase sintering of Si3N4 powder com-pacts with oxide additives and the development of complex microstructures in which high aspect ratio β-Si3N4 grains and intergranular glass phase increase the resistance to crack propagation leading to the highest fracture toughness, combined with high strength, of any ceramic available. Silicon nitride has been investigated as a bioceramic for use in bearings for hip and knee replacements. Si3N4 has very favorable tribological properties when it articulates against polyethylene, the dominant material for bearing surfaces in prosthetic joints. It is biocompatible, non-toxic, and corrosion-resistant, all of which are crucial in medical implants. The porous form of Si3N4 may be suitable for devices where bone ingrowth is necessary for durable biological fixation. Further developments in silicon nitride ceramics for biomedical applications may be expected through a better understanding of grain boundary chemistry and its effects on microstructure, surface chemistry, and biological interactions.

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Why is it important?

Today, silicon nitride is one of the brightest shining stars in the field of bioceramics: besides its load-bearing qualities, it has an exceptionally interesting bioactivity, demonstrating not only osteoconductivity but also both antibacterial and antiviral effects.

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