Performance comparison between silicon carbide ceramics and silicon nitride ceramics

In the following comparative analysis of silicon carbide and silicon nitride ceramics, we will systematically explain the core differences between the two from three dimensions: physical properties, chemical properties, and application fields.

I. Differences in physical properties

Mechanical properties

Silicon carbide: higher hardness (Mohs 9.2), but lower fracture toughness (3-4 MPa·m¹/²)

Silicon nitride: slightly lower hardness (Mohs 8.5), excellent fracture toughness (6-7 MPa·m¹/²)

Thermal properties

Parameters Silicon carbide Silicon nitride Thermal conductivity 120-200 W/m·K 15-30 W/m·K Thermal expansion coefficient 4.5×10⁻⁶/℃ 3.2×10⁻⁶/℃

II. Comparison of chemical stability

Oxidation resistance: Silicon carbide will form an oxide layer above 1400℃, and silicon nitride will begin to oxidize at 1300℃

Corrosion resistance: Silicon nitride is more resistant to acid/alkali solutions, and molten alkali metals easily corrode silicon carbide

Ceramic balls

III. Typical application fields

Core scenarios of silicon carbide

High-temperature structural parts: gas turbine blades (continuous operation at 1600℃)

Semiconductor devices: Power module substrate (thermal conductivity is 6 times that of silicon nitride)

Nuclear industry: fuel cladding material (small neutron absorption cross section)

Advantage areas of silicon nitride

Precision bearings: All-ceramic bearings have a life of more than 100,000 hours.

Biomedical: Artificial joints (friction coefficient is only 0.002)

Electronic packaging: High-frequency circuit insulation substrate

IV. Process cost difference

Silicon carbide sintering requires a high temperature of more than 2100℃, while silicon nitride can be densified at 1700-1900℃, but the latter requires a nitrogen protective atmosphere. The current raw material cost of silicon carbide is about 60% of that of silicon nitride, but the processing cost is about 40% higher.

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