Characteristics and Applications of Silicon Nitride Ceramics

Silicon nitride ceramic (Si₃N₄) is a high-performance non oxide ceramic known for its ultra-high strength, excellent thermal shock resistance, wear resistance, and chemical stability. It is widely used in the aerospace, automotive industry, and high-end equipment manufacturing fields.

1. What is silicon nitride ceramic?

Silicon nitride ceramics are advanced ceramic materials made by high-temperature reaction sintering of silicon (Si) and nitrogen (N), and their characteristics include:

✔  High strength and toughness (flexural strength 800-1000MPa, fracture toughness 6-8 MPa · m ²)

✔  Super strong thermal shock resistance (Δ T>800 ℃ without rupture)

✔  High temperature resistance (long-term use temperature of 1400 ℃)

✔  Low density (3.2g/cm ³, 60% lighter than steel)

Preparation process

Reaction sintering (RBSN): porous structure, low cost

Hot pressing sintering (HPSN): high density, optimal performance

Pressure sintering (GPSN): complex shapes, mainstream commercialization

2. Performance characteristics of silicon nitride ceramics

(1) Mechanical performance

Hardness: Hv5600-1800 (close to tungsten carbide)

Bending strength: HPSN can reach 1000MPa (comparable to alloy steel)

Elastic modulus: 310GPa (strong deformation resistance)

(2) Thermal properties

Maximum operating temperature: 1400 ℃ (long-term)

Thermal conductivity: 20-30W/(m · K)

Thermal expansion coefficient: 3.2 × 10 ⁻⁶/° C

(3) Chemical stability

Corrosion resistance: resistant to all acids and bases except hydrofluoric acid (pH 1-14)

Antioxidant: Stable in air below 1200 ℃

3. Application of silicon nitride ceramics

(1) High end industry

Turbine rotor: High temperature resistant blades for aircraft engines (reduced weight by 40%)

Bearing ball: with a lifespan of over 100000 hours under non lubricated working conditions

(2) Energy and Transportation

Diesel engine components: turbocharger heat-resistant vortex shell (resistant to 950 ℃ exhaust gas)

Fuel cell: bipolar plate (conductive+corrosion-resistant)

(3) Tools and Medical Care

Cutting tools: high-speed machining of cast iron/nickel based alloys

Orthopedic implants: biologically inert hip prosthesis

4. Technological frontiers

Nanocomposite ceramics: Si₃N₄ - SiC composite material (hardness Hv2200)

3D printing technology: direct molding of complex structure turbine blades

Transparent Silicon Nitride: Laser Window Material (Laboratory Stage)

Summary

Silicon nitride ceramics have become the preferred material under extreme working conditions due to their perfect balance of strength, toughness, and temperature resistance, continuously promoting innovation in high-end manufacturing technology!