3M Technical Ceramics
Zweigniederlassung der 3M Deutschland GmbH

Chemical properties

Chemical formula Si₃N₄
Molecular weight 140.28 g/mole
Crystalline structure hexagonal and infrequent trigonal crystals
  • The sintered material contains an oxide grain boundary phase, which is frequently amorphous and partially crystalline.
  • High chemical resistance is only slightly moistened by non-ferrous metal melts.

Physical properties

Specific Weight 3.26 g/cm³
Very high fracture toughness (hence highest rigidity among engineered ceramic materials) ZrO₂ to 1,300 MPa
Very high flexural strength 800 MPa
High modulus of elasticity 300 GPa

Thermal properties

  • Low thermal expansion
  • Very good resistance to temperature change
  • Maximum working temperature 1,200°C
  • Moderate thermal conductivity

Manufacture and form

Si₃N₄ components are manufactured via liquid phase sintering from ground subµ-Si3N4 finest powder, which is mixed with oxidic sinter additives, processed with normal ceramic shaping methods and sintered at 1,800 to 1,900 °C in a nitrogen atmosphere at pressures of up to 100 bar. By using the normal ceramic-shaping method, varying component shapes are possible.

Processing of sintered components with diamond tools is possible because of the hardness and toughness, particularly to achieve reduced geometric tolerances.

Due to its rare combination of properties, silicon nitride is used in circumstances where highest levels of mechanical stress and/or extreme thermal cycling occur. In addition, silicon nitride combines high wear resistance with high corrosion and temperature resistance at low specific weight. This makes silicon nitride particularly suitable for high-temperature applications in engineering.

  • Roller elements for bearings under high stress
  • Slide bearings for applications subject to thermal and corrosive stress in the exhaust systems of combustion engines
  • Ball bearings for high stresses at low friction
  • Wear parts (e.g. in paper machines)