Boron Nitride Ceramics

1. High-Temperature Resistance

   • High melting point (~3000°C), stable for long-term use in inert atmospheres.

   • Maintains excellent electrical insulation and chemical inertness at elevated temperatures.

2. Thermal Conductivity & Electrical Insulation

   • h-BN has high thermal conductivity (≈30 W/m·K) while remaining electrically insulating, making it ideal for high-temperature electronic heat dissipation.

   • c-BN approaches diamond in hardness but offers superior thermal stability (resists oxidation up to 1400°C).

3. Lubricity

   • h-BN has a layered structure similar to graphite, providing low friction (coefficient: 0.2–0.4) and serving as a high-temperature lubricant.

4. Chemical Stability

   • Resistant to acids, alkalis, and molten metals, with better oxidation resistance than graphite.

5. Mechanical Properties

   • c-BN ranks second only to diamond in hardness but exhibits lower brittleness, making it suitable for machining ferrous materials.

II. Applications

1. High-Temperature Environments

   • Crucibles, thermocouple protection tubes, rocket nozzle linings.

2. Electronics Industry

   • Heat dissipation substrates for integrated circuits, high-voltage insulating components, 5G device thermal films.

3. Machining & Tooling

   • c-BN-based ultra-hard cutting tools for precision machining of high-hardness steels.

4. Lubrication

   • High-temperature bearings, release agents (e.g., in metal casting, glass molding).

5. Aerospace

   • Ablation-resistant components, thermal shielding for spacecraft.

6. Nuclear Industry

   • Neutron-absorbing materials (due to boron’s high neutron capture cross-section).

7. Other Applications

   • Cosmetic additives (h-BN is non-toxic and smooth), LED substrates, etc.

Summary: Boron nitride ceramics, with their unique combination of high-temperature stability, thermal conductivity, electrical insulation, and lubricity, are indispensable in extreme environments and advanced industrial applications.