Hexagonal Boron Nitride (H BN) Sheets for High-Temperature Electrical & Thermal Insulation

Hexagonal Boron Nitride Sheet Applications

• h BN Sheets in Vacuum Furnaces and Brazing Systems

  ✅Key Advantages

  1. High-temperature electrical insulation – h BN sheets withstand around 800–1000°C in vacuum furnaces exposed to residual oxygen, while in inert hot zones they can operate close to 2000°C.
  2. Stable thermal barrier and heat spreader – thermal conductivity in the 30–70 W/m·K range supports efficient heat transfer while limiting local hot spots in fixtures and walls.
  3. Machined plates for complex fixtures – h BN sheets can be machined into door liners, support plates and mask plates that match brazing fixtures and component geometries.

  ✅ Problem Solved

  A vacuum brazing furnace manufacturer replacing mica or fiber-based insulation with h BN sheets in the hot zone reported that fixtures maintained dimensional stability through more than 200 heating cycles without visible cracking, while previous materials needed partial replacement after 50–80 cycles. The higher thermal conductivity also reduced heating and cooling gradients, contributing to more uniform brazed joints and a lower scrap rate on multi-part loads.

• h BN Sheets in Non-Ferrous Metal Melting and Casting

  ✅Key Advantages

  1. Non-wetting interface with molten aluminum and magnesium – h BN offers low wettability with several non-ferrous melts, reducing build-up on chutes and contact plates.
  2. Dimensional stability at casting temperatures – stable properties above 700–800°C allow h BN sheets to work near typical aluminum and magnesium melt temperatures.
  3. Electrical and thermal separation – when combined with heaters or sensors near the melt, h BN sheets insulate electrical components while still allowing heat transfer.

  ✅ Problem Solved

  In a gravity casting line for aluminum components, replacing steel backing plates with h BN sheets between the mold and heater block helped reduce sticking of solidified metal on contact surfaces. After the change, the foundry recorded fewer forced cleaning shutdowns and reported that plate replacement intervals increased from roughly three months to more than six months, with lower labour time spent on manual scraping and surface reconditioning.

• h BN Sheets in High-Voltage Power Supplies and Plasma Systems

  ✅Key Advantages

  1. High dielectric strength at elevated temperature – h BN insulation grades show dielectric breakdown strength close to 80–95 kV/mm, enabling compact insulation paths in power supplies and plasma sources.
  2. Low dielectric constant and low loss – relative permittivity around 4–5 and low loss tangent help limit RF and high-frequency losses in certain designs.
  3. Thermal management of hot components – thermal conductivity significantly above that of many polymer insulators supports stable component temperatures and improved service life.

  ✅ Problem Solved

  A plasma power supply builder used h BN sheets as insulating heat spreaders under high-voltage components mounted in a compact enclosure. After switching from conventional polymer laminates to BN ceramic sheets, internal hot-spot temperatures dropped by around 10–15°C at similar load, and the number of insulation-related failures during burn-in decreased over several hundred units shipped, according to the internal qualification report.

Usage Guide — h BN Sheets Installation and Handling

• Installation

  Verify that the specified thickness, flatness and hole pattern match the mating metal or ceramic parts before installation.
  Mount h BN sheets on flat, clean surfaces, using designed clamping areas to avoid high local stress near edges and holes.
  When clamping with metal fasteners, use washers or pads where possible to distribute stress and reduce chipping.

• Operation

  Use h BN sheets within the agreed temperature window for the chosen grade and furnace atmosphere.
  In oxidizing air, avoid continuous operation near the upper stability limit; in inert or vacuum service, respect furnace and material limits defined in the datasheet.
  Avoid rapid temperature shocks that exceed the thermal shock capability of the sheet, especially for thick plates.

• Storage

  Store h BN sheets in dry, clean indoor conditions, away from strong alkaline chemicals and molten alkali salts that can attack BN.
  Keep sheets in their protective packaging until just before machining or installation to reduce accidental chipping.

• Cleaning

  For dry contamination, use soft brushes or non-metallic scrapers; avoid hammering or impact tools on edges.
  For molten metal residues, allow parts to cool completely and use gentle mechanical cleaning; do not apply aggressive alkaline or fluoride-containing cleaners that can attack BN.

• Typical misuse points and how to avoid them

  1. Over-tightening bolts through h BN sheets
  Problem: Cracks forming from bolt holes after a few cycles.
  Solution: Use torque-limited tightening, larger washers and, if needed, design additional support faces to spread load.

  2. Thermal shock from rapid quenching
  Problem: Edge chipping or plate fracture when moving directly from high temperature into cold air.
  Solution: Introduce controlled cooling ramps and avoid forced air or liquid quenching directly onto h BN sheets.

  3. Using the wrong grade for oxidizing atmospheres
  Problem: Progressive surface oxidation in air above the recommended temperature, resulting in powdering surfaces.
  Solution: Confirm grade suitability and limit time at high temperature in air; for long-term high-temperature use, prefer inert gas or vacuum conditions.

Hexagonal Boron Nitride Sheet FAQ

1. Q: What are h BN sheets used for in industrial equipment?
   A: h BN sheets are used as high-temperature electrical insulation, thermal management plates and non-wetting contact surfaces in vacuum furnaces, thermal processing systems, non-ferrous metal equipment and high-voltage power or plasma systems
2. Q: How hot can h BN sheets operate?
   A: Typical hot-pressed h BN sheets can operate up to around 800–1000°C in oxidizing air and can approach about 2000°C in inert or vacuum atmospheres, depending on grade and design.
3. Q: Are h BN sheets electrically insulating?
   A: Yes, hexagonal boron nitride sheets are strong electrical insulators with high volume resistivity and dielectric strength, which allows them to separate high-voltage parts while still conducting heat away from components.
4. Q: What is the difference between h BN sheets and PBN sheets?
   A: h BN sheets are usually hot-pressed bulk ceramics that are machinable and available in relatively thick plates, while PBN sheets are pyrolytic boron nitride deposited in thin, dense layers with extremely high purity for ultra-high vacuum and semiconductor applications.
5. Q: Can hexagonal boron nitride sheets replace alumina or mica plates?
   A: In many high-temperature and vacuum applications, h BN sheets can replace alumina or mica plates where higher thermal conductivity, better machinability or non-wetting behaviour with molten metals is needed; final selection depends on temperature, atmosphere and mechanical loads.

Hexagonal Boron Nitride Sheet Reviews

• ⭐️⭐️⭐️⭐️⭐️
  We switched several furnace fixtures to machined h BN sheets from ADCERAX. The plates fit our existing frames without redesign, and after more than one year of production the insulation surfaces have stayed stable through repeated cycles.
  David K. – Engineering Manager, Thermal Systems OEM (Germany)
• ⭐️⭐️⭐️⭐️⭐️
  Using boron nitride ceramic sheets as contact plates around the launder has reduced cleaning time between casting campaigns. Pricing from this supplier is reasonable for a high-temperature material, and batch-to-batch consistency has been good.
  Maria S. – Operations Director, Aluminum Casting Plant (Spain)
• ⭐️⭐️⭐️⭐️⭐️
  We use thin h BN sheets as insulating heat spreaders in a high-voltage module test stand. The combination of thermal conductivity and insulation allowed us to simplify the design and keep device temperatures within the target window.
  Kenji T. – R&D Engineer, Power Electronics Company (Japan)
• ⭐️⭐️⭐️⭐️⭐️
  For repair projects we often need small quantities of custom-shaped BN plates. ADCERAX has been able to machine h BN sheets according to our sketches and supply them in low volumes, which helps us keep lead times under control for our customers.
  Robert L. – Owner, Vacuum Furnace Service Company (USA)