What are the material properties of silicon nitride ceramics?
Release time: 2025-04-15
Silicon nitride ceramic (Si₃N₄) possesses high strength, low density, high-temperature resistance
Silicon nitride ceramic (Si₃N₄) possesses high strength, low density, high-temperature resistance, a low coefficient of thermal expansion, a self-healing oxide layer that inhibits creep, and resistance to irradiation and chemical stability. These properties make silicon nitride ceramic excel in numerous applications.
Specific Properties
High Strength and Low Density: The flexural strength of silicon nitride ceramic is between 800-1200 MPa, 2-3 times that of alumina, and close to that of some alloy steels. Its density is 3.2-3.4 g/cm³, only 40% that of steel.
High-Temperature Resistance: Silicon nitride ceramic can be used continuously at 1200℃ in air and for short periods at 1600℃. Its coefficient of thermal expansion is only 2.8-3.2×10⁻⁶/℃ (room temperature to 1000℃), far lower than that of stainless steel and alumina ceramic.
Low Thermal Expansion: Under severe temperature changes, the thermal expansion of silicon nitride ceramic can be controlled to within 0.05%, and the dimensional fluctuation rate is less than 0.3%.
Self-Healing Oxide Layer Inhibits Creep: When the temperature rises above 800℃, an amorphous SiO₂ layer forms on the surface of the silicon nitride, dynamically filling microcracks and inhibiting oxygen diffusion, reducing the high-temperature creep rate to 1×10⁻⁹s⁻¹ (1200℃).
Irradiation Resistance and Chemical Stability: The high bond energy (4.5 eV) of the Si-N bond gives silicon nitride excellent irradiation stability, with a volume expansion rate <0.2% under a 10⁷Gyγ ray dose. At the same time, its resistance to strong acids (except hydrofluoric acid), strong alkalis, and oxidizing/reducing atmospheres prevents corrosion-induced dimensional distortion.
Excellent Electrical Properties: Silicon nitride ceramic maintains its insulating properties even at high temperatures, with a volume resistivity of 10¹⁴-10¹⁶Ω·cm and a dielectric constant of 8-9.
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