Hexagonal boron nitride (h-BN) is the only ceramic that's fully machinable with conventional metal-cutting tooling, lubricious like graphite, electrically insulating, and stable to 2000°C in inert atmosphere. Used as crucibles for molten metals, release coatings for non-stick glass and metal forming, and plasma-facing insulators in semiconductor equipment.
Property values below are typical for our standard hexagonal BN (h-BN) and pyrolytic BN (PBN) production grades. h-BN is the workhorse machinable grade; PBN is the higher-purity, higher-temperature grade for semiconductor and aerospace use.
| Property | Unit | Hot-Pressed h-BN | Pyrolytic BN (PBN) | BN Composite |
|---|---|---|---|---|
| Density | g/cm³ | 2.10 | 2.20 | 2.30 |
| Max Service Temp (inert) | °C | 2000 | 2200 | 1800 |
| Max Service Temp (air) | °C (oxidation) | 900 | 900 | 1000 |
| Thermal Conductivity (∥ basal) | W/m·K | 60 | 62 | 40 |
| Thermal Conductivity (⊥ basal) | W/m·K | 30 | 2 | 20 |
| Thermal Expansion | ×10⁻⁶/K | 1.0 | 0.7 | 3.5 |
| Dielectric Strength | kV/mm | 50 | 60 | 40 |
| Volume Resistivity (20°C) | Ω·cm | 10¹⁴ | 10¹⁶ | 10¹³ |
| Flexural Strength | MPa | 50 | 100 | 200 |
| Machinable (carbide tooling) | — | Yes | Yes | Yes |
BN's most common product forms are bulk crucibles for molten metals, custom-machined parts for plasma insulators and break rings, and BN powder/spray release coatings for glass and metal forming. Each leverages different BN properties.
BN crucibles for handling molten aluminum, magnesium, gallium, and evaporation-grade metals. BN is non-wetting to most molten metals — the deposit doesn't stick, the crucible doesn't contaminate the melt. Used heavily in vacuum evaporation and aluminum refining.
Machined h-BN parts for semiconductor plasma insulators, Czochralski crystal-growth break rings, electron-beam window plates, and high-temperature seals. Conventional carbide tooling — same machining workflow as machinable graphite.
h-BN powder and aerosol spray for non-stick release coatings on glass-forming molds, metal extrusion dies, and welding splash protection. Stable to 900°C in air, doesn't carbonize like graphite-based releases.
BN ships into six application categories most often — common thread is high temperature in inert/vacuum atmospheres, non-wetting to metals/glass, or electrical insulation at high temperature.
BN-TiB₂ composite evaporation boats and crucibles for vacuum deposition of aluminum, magnesium, and other reflective metal coatings. Standard equipment in metallized film production.
BN break rings, baffle plates, and isolators for silicon and compound-semiconductor crystal growth furnaces. Doesn't contaminate molten silicon, withstands the thermal cycling of pull-and-cool operation.
h-BN and PBN insulator rings, focus rings, and chamber liners for plasma etch and CVD chambers. Doesn't trigger plasma instabilities, withstands fluorine plasma chemistries better than most oxide ceramics.
h-BN spray and powder as a non-stick release coat on glass-forming molds (e.g. precision optical glass molding, container glass pressing). Lower carbon contamination than graphite-based releases.
BN coatings on aluminum casting dies, extrusion dies, and ladles. Non-wetting to molten aluminum prevents drag-out, surface defects, and die soldering. Standard release agent in high-end aluminum production.
PBN insulator parts for ion thruster discharge chambers, traveling-wave tube collector isolators, and high-temperature aerospace electronics. Anisotropic thermal conductivity used as a design feature, not a limitation.
BN is the only ceramic that combines machinability + electrical insulation + 2000°C inert-atmosphere stability. Pick it when those properties cluster together — otherwise alumina or graphite are usually more cost-effective.
A European precision optical glass molder was struggling with carbon-particle defects in their molded aspheric lens production — graphite-based mold release was breaking down at the 700°C molding temperature and leaving carbon residue on lens surfaces. Switching to h-BN aerosol spray cut carbon defect rate by 99% in the first month and extended mold service life 4×.
Direct answers from our application team. Email engineering@ceramitell.com with your application or drawing for a tailored response.