Silicon nitride (Si3N4) is a chemical compound of the elements, silicon and nitrogen. It is one of the leading technical ceramic materials available on the market and has similar properties like silicon carbide. Over the years, this material has been effectively utilized in a variety of applications ranging from roller bearings in skateboards (Figure 1) to automotive engine components.
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Figure 1. Roller bearings for skateboard
Properties of Silicon Nitride
Silicon nitride has unique and remarkable properties. In fact, bearings made from this material have been utilized in the main engines of the Space Shuttle. It is one of the few monolithic ceramic materials that can withstand extreme thermal shock and thermal gradients produced in oxygen and hydrogen rocket engines. It proved extremely reliable across the entire Space Shuttle programme.
Silicon nitride offers a number of benefits, such as low friction, high wear and chemical resistance, high temperature capability and high electrical resistivity. It is nonmagnetic, has low specific weight, and offers long service life. Recently, silicon carbide has been used in the brake discs of the McLaren P1, a highly sophisticated road car.
However, despite its various benefits, nitrides are very hard wearing and need diamond-grinding techniques to process once fired. Just like silicon carbide, silicon nitride is specifically utilized for those applications where physical wear is an important factor. At Precision Ceramics, both silicon nitride and silicon carbide are utilized for a range of technical components for wide field of applications.
Silicon Nitride in Automotive Industry
Silicon nitride is predominantly used in the automotive industry for manufacturing engine components. In diesel engines, glow plugs made from silicon nitride enable faster start-up; swirl chambers or pre-combustion chambers contribute to lower noise and lower emissions.
In turbochargers, silicon nitride helps in reducing engine lag and emissions; in petrol engines, it is utilized for rocker arm pads to reduce wear; and in exhaust gas control valves, the material allows for increased acceleration. It has been estimated that over 300,000 sintered silicon nitride turbochargers are developed each year.
Silicon Nitride Bearings
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Figure 2. Silicon nitride bearings
Since silicon nitride is a bearing material, it is widely utilized for full ceramic bearings as well as for hybrid ceramic bearings where ceramic balls are effectively employed in tandem with steel races. Since silicon nitride ball bearings (Figure 2) are harder than metal, contact with the bearing track is significantly reduced. This results in up to 80% less friction and an extended service life between 3 to 10 times longer than steel.
Conclusion
Silicon nitride also offers excellent corrosion resistance and enables high temperature operation. Silicon nitride ball bearings are generally found in wind turbines, industrial bearings, high end automotive bearings, skateboards, bicycles and rollerblades. At Precision Ceramics, silicon nitride is ranked high in the company’s wide range of technical ceramics.
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This information has been sourced, reviewed and adapted from materials provided by Precision Ceramics.
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