About Boron Nitride

Boron Nitride is an advanced synthetic ceramic material available in solid and powder form. Its unique properties – from high heat capacity and outstanding thermal conductivity to easy machinability, lubricity, low dielectric constant and superior dielectric strength – make boron nitride a truly outstanding material.

In its solid form, boron nitride is often referred to as “white graphite” because it has a microstructure similar to that of graphite. However, unlike graphite, boron nitride is an excellent electrical insulator that has a higher oxidation temperature. It offers high thermal conductivity and good thermal shock resistance and can be easily machined to close tolerances in virtually any shape. After machining, it is ready for use without additional heat treating or firing operations.

In inert and reducing atmospheres, the AX05 grade of Boron Nitride grades will withstand temperatures over 2,000°C.   It is commonly used as an insulator in contact with tungsten and graphite electrodes at those temperatures.

All Boron Nitride grades can be used in oxidizing atmospheres up to 750°C. It is not wet by most molten metals and slags and can be used in contact with most molten metals including aluminum, sodium, lithium, silicon, boron, tin, germanium, and copper.

Boron Nitride is available in a variety of solid grades, differentiated by binder and composite – A, AX05, HP, HPL, M, M26 and ZSBN.

Boron Nitride Info Sheet (PDF)

Grade AX05 is considered the pinnacle of Boron Nitride materials and is the highest purity hexagonal Boron Nitride (hBN) available at 99.7%+. It is available in slabs up to 490mm x 490mm x 35-40mm thick, hollow shapes such as crucibles that are 300mm dia x 300+ mm tall, or other machined shapes in between. Its high purity enables it to be used in inert or vacuum environments in excess of 2000°C, where it still remains an outstanding electrical insulator with a dielectric strength of >40kV/mm. This makes it an excellent choice for applications where high temperature capabilities and corrosion resistance are important. AX05 is unique because it does not depend on B2O3 or other binders for mechanical integrity. Instead, it is a diffusion bonded ceramic and is non-wet by almost all molten metals. This ultra-high purity allows for applications where other hot pressed boron nitride solids with binders could fail, such as crucibles for high-purity molten metals. Due to its high thermal conductivity and its close-to-zero thermal expansion, AX05 literally cannot be thermal shocked.
Boron Nitride AX05 Grade Info Sheet (PDF)
B2O3-bonded, A Grade is the oldest form of hot-pressed Boron Nitride. Specified into applications 50+ years ago, A Grade still finds a substantial replacement business as relatively high-temperature insulators in legacy semiconductor equipment and defense markets. Components up to 410mm x 495mm x 245mm can be produced. However, its B2O3 binder is hygroscopic and care must be taken to ensure components are isolated from moisture during storage and use. Precision Ceramics USA uses many methods of packaging to maintain the high quality of its machined components.
Boron Nitride A Grade Info Sheet (PDF)
HP Boron Nitride is the workhorse grade of BN, useful when low thermal expansion, high thermal shock resistance, and strong electrical properties are required. To minimize the moisture issues of A Grade, HP was developed with a calcium borate glass binder. It is available in shapes up to 410mm x495mm x 245mm. With its excellent machinability and good to over 1000°C in inert or vacuum, it finds many diverse applications.
Designed by Saint-Gobain for a specific semiconductor equipment OEM, HPL has many of the properties of HP Grade, except a somewhat increased temperature range. It is primarily marketed in Asia, but with growing application in the US. It is softer than HP Grade due to its lower binder content and still very machinable to complex shapes and tight tolerances.
Unique in the hBN world, M26 is a composite of very specific hBN powders in a silica matrix. With 60% hBN and 40% semiconductor grade SiO2, M26 combines hardness and machinability with a somewhat lower thermal conductivity. The silica (SiO2) binder system contributes to its excellent moisture/thermal shock resistance. These grades can operate up to 1400°C. Grade M is somewhat more resistant to moisture and has a MIL-I-10A grade of L542, a test requiring immersion in water for 48 hours prior to testing at elevated frequencies. While these materials are excellent thermally, it is their strength combined with electrical properties that are most in demand. Their high dielectric strength (>40KV/mm) along with a low dielectric constant k (<4) in a machinable, hard ceramic are invaluable for microwave environments in the GHz ranges.
Boron Nitride M26/M Grades Info Sheet (PDF)
ZSBN is unique because it is a composite material that combines the best properties of hot-pressed boron nitride with the non-reactivity and strength/wear resistance of zirconia. Originally developed for break rings for horizontal continuous casters, its unique thermal, chemical, electrical, wear, and machinability properties permit a wide variety of molten-metal-contact applications. hBN is an inherently soft material. However, with ZSBN’s hard ZrO2 particles evenly dispersed with BN platelets in the hard borosilicate glass matrix, it has great wear properties added to the inherent non-wetting aspects of the hBN. ZSBN is a uniquely high-performing solid that is especially suited for molten metal applications such as continuous casting break rings, where wear resistance and thermal conductivity are essential. There are many applications in molten-metal atomizing nozzles, glass contact wear components, and countless guides and rollers in diverse light-metal baths of Zn, Mg and Al. And increasingly, lithium, as battery development continues.
Boron Nitride ZSBN Grade Info Sheet (PDF)

General Hexagonal Boron Nitride Properties

To make solid shapes, hBN powders and binders are hot-pressed in billets up to 490mm x 490mm x 410mm at pressures up to 2000 psi and temperatures up to 2000°C. This process forms a material that is dense and easily machined and ready to use. It is available in virtually any custom shape that can be machined and has unique characteristics and physical properties which make it valuable for solving tough problems in a wide range of industrial applications.

  • Excellent thermal shock resistance
  • High electrical resistivity – excluding aerosols, paints, and ZSBN
  • Low density
  • High thermal conductivity
  • Anisotropic (thermal conductance is different in different planes relative to pressing direction)
  • Corrosion resistant
  • Good chemical inertness
  • High temperature material
  • Non-wetting
  • High dielectric breakdown strength, >40 KV/mm
  • Low dielectric constant, k=4
  • Excellent machinability

Technical Boron Nitride Properties

* Note – When solid boron nitride is hot pressed, the crystal structure of the material orients itself. This results in anisotropic physical and thermal properties; meaning they vary depending on the orientation of the material relative to hot pressing direction (parallel or perpendicular).

Boron Nitride Applications

  • Break rings for continuous casting of metals
  • Break rings for continuous casting of metals
  • Heat treatment fixtures
  • High temperature lubricant
  • Molds/mold release agent
  • Molten metals and glass casting
  • Nozzles for transfer or atomization
  • Laser nozzles
  • Nuclear shielding
  • Induction heating coil supports
  • Spacers
  • High-temperature & high-voltage electrical insulators
  • Furnace supports which require electrical resistivity
  • Crucibles and containers for high purity molten metals
  • Radar components and antenna windows 
  • Ion thruster discharge channels

Boron Nitride for Thermal Management of Electronic Devices

Boron Nitride is one of the few materials that offers electrical insulation and high thermal conductivity. This makes BN extremely useful in high power electronic applications in heat sink and heat spreader applications. Other materials that are commonly used are Aluminum Nitride, beryllium oxide, and sometimes Alumina – however, all of these materials are significantly more difficult to machine into intricate shapes.

Boron Nitride Machining

Hexagonal boron nitride can be machined into highly complex geometries with very tight tolerances. Precision Ceramics has 3, 4 and 5 axis CNC machining capabilities and over 20 years of experience creating custom boron nitride components.

Buy Hexagonal Boron Nitride

Precision Ceramics is your Boron Nitride machining specialist for your technical ceramic prototyping & manufacturing needs; we are always happy to use our many years of advanced ceramics experience to provide advice on materials, design, and application. If you would like to buy Boron Nitride plates, bars, rods, tubes, Aerosol Sprays, Paintable Coatings, Industrial Powders, or custom machined parts, please contact us and one of our experts will be happy to assist you.