Hexagonal boron nitride h-BN
BN, hexagonal boron nitride (one boron and one nitrogen atom per formula unit, bonded in graphite-like layers). Hot-pressed grades contain a binder: calcium borate in NASA's HP grade, B2O3 in the SAM BN-BO Grade A · CAS 10043-11-5
Also known as Grade A, HP, AX05, PT110
Hexagonal boron nitride (h-BN) is a graphite-like layered form of BN.
Evidence level
2 of 5
Lab-measured
- 0Predicted only. No one has made it, or no measurement exists.
- 1Calculated. Only calculated or predicted values from sources.
- 2Lab-measured. Measured properties with their conditions stated.
- 3Space-relevant tests. Measured in conditions relevant to space, such as vacuum or atomic oxygen.
- 4Ground-qualified. Qualified for an application on the ground.
- 5Flown or field-proven. Flight or field results exist.
Insulate electrically
88 kV/mm
Carry heat
30 to 34 W/(m·K)
Work hot
850 °C in air
Recipe, share of the weight
- B not statedBoron
- N not statedNitrogen
Best for
Electrical insulation and microwave or high-temperature insulating parts, where the 88 kV/mm dielectric strength and the 850 °C air limit of Grade A matter
Weakest at
Strength across or at high temperature: HP bending strength parallel to pressing falls from 39.7 MPa at 25 °C to 9.8 MPa at 600 °C, and oxidation in ambient air begins near 900 °C
Risk at a glance
- People Low. Mixed notifications
- If it fails High. Bending failure at high temperature, parallel to pressing
- Corrosion Moderate. Oxidation of h-BN in air first shows at about 900 °C after 20 minutes, as shallow pits.
Quick facts: h-BN
| Property | Value | Basis |
|---|---|---|
| Density | 2 to 2.1 g/cm³ | 2 sourced values across conditions |
| Young's modulus | 47 to 80 GPa | 4 sourced values across conditions |
| Thermal conductivity | 30 to 600 W/(m·K) | 6 sourced values across conditions |
| Thermal expansion (CTE) | 0.4 to 3.1 ppm/K | 2 sourced values across conditions |
| Maximum service temperature | 850 to 1,200 °C | 2 sourced values across conditions |
What is the density of Hexagonal boron nitride (h-BN)?
Hexagonal boron nitride (h-BN) has a density of 2 to 2.1 g/cm³. The range covers 2 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is the thermal conductivity of Hexagonal boron nitride (h-BN)?
Hexagonal boron nitride (h-BN) has a thermal conductivity of 30 to 600 W/(m·K). The range covers 6 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is the coefficient of thermal expansion of Hexagonal boron nitride (h-BN)?
Hexagonal boron nitride (h-BN) has a coefficient of thermal expansion of 0.4 to 3.1 ppm/K. The range covers 2 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is the Young's modulus of Hexagonal boron nitride (h-BN)?
Hexagonal boron nitride (h-BN) has a Young's modulus of 47 to 80 GPa. The range covers 4 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is the maximum service temperature of Hexagonal boron nitride (h-BN)?
Hexagonal boron nitride (h-BN) has a maximum service temperature of 850 to 1,200 °C. The range covers 2 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What are the other names and codes for Hexagonal boron nitride (h-BN)?
Hexagonal boron nitride (h-BN) is also written as Grade A, HP, AX05, PT110. Each code is printed in the source listed beside it in the designations table.
What is Hexagonal boron nitride (h-BN) used for?
Uses recorded in the sources include Insulators and components in space electric propulsion; High-voltage electrical insulator with high thermal conductivity; Microwave components and high-temperature electrical insulators.
Why it exists
h-BN is an electrical insulator that also conducts heat well for an insulator. In Precision Ceramics Grade A, a hot-pressed grade, the dielectric strength is 88 kV/mm and the thermal conductivity is 30 W/(m·K) parallel and 34 W/(m·K) perpendicular to pressing. Its air limit is 850 °C. These properties suit microwave parts and high-temperature insulators. NASA tested hot-pressed h-BN grades for space electric propulsion, where parts must insulate electrically and thermally.
Where it's used
Electric propulsion
NASA Glenn and JPL tested several commercial hot-pressed h-BN grades for space electric propulsion, where parts must insulate electrically and thermally.
Microwave and high-temperature insulators
Precision Ceramics lists microwave components, radar components and high-temperature electrical insulators among the uses of Grade A.
Solid lubricant
Wikipedia says h-BN is a good lubricant up to 900 °C, including in oxidizing atmospheres and in vacuum.
Recipe
BN, hexagonal boron nitride (one boron and one nitrogen atom per formula unit, bonded in graphite-like layers). Hot-pressed grades contain a binder: calcium borate in NASA's HP grade, B2O3 in the SAM BN-BO Grade A
h-BN is the hexagonal form of boron nitride, with boron and nitrogen bonded in layers and van der Waals forces between layers. Its density is 2.1 g/cm3 (Wikipedia). BN has a molar mass of 24.82 g/mol (PubChem). Hot-pressed ceramic grades are made by hot pressing h-BN powder with a binder: NASA's HP grade contains a calcium borate binder and a BN phase of 98 wt % by Rietveld refinement, and Stanford Advanced Materials lists the Grade A binder as B2O3 (SAM).
| Ingredient | Share of the weight | What it does |
|---|---|---|
| Boron B | not stated | One boron atom per formula unit, bonded to nitrogen within each layer |
| Nitrogen N | not stated | One nitrogen atom per formula unit, bonded to boron within each layer |
Weight shares are as printed in the sources.
What it can do
Insulate electrically
88 kV/mm
measured
Grade A has a DC dielectric strength of 88 kV/mm, and a dielectric constant of 4.6 parallel and 4.2 perpendicular at 1 MHz.
Carry heat
30 to 34 W/(m·K)
measured
Grade A conducts heat at 30 W/(m·K) parallel and 34 W/(m·K) perpendicular to pressing. The NASA HP grade gives 33 and 31 W/(m·K).
Work hot
850 °C in air
measured
Grade A is rated to 850 °C in air and 1200 °C in an inert atmosphere, per the datasheet. These are manufacturer figures, not component allowables.
How it compares
In this profile the in-plane thermal conductivity of hot-pressed grades, 30 to 34 W/(m·K) for Grade A and 33 for HP, is about one-twentieth of the 600 W/(m·K) that Wikipedia gives for h-BN along the basal planes. Pressing and binder content set how much of that ideal conductivity a grade keeps. The strength also changes most with direction: Grade A reaches 94 MPa parallel and 65 MPa perpendicular, while the HP grade reverses that order at 39.7 and 70.5 MPa.
The same measurements for each material, so you can compare them. Each row names the key condition under the value; the full conditions and methods are in the numbered notes under Technical details. Other materials are shown beside it; each was measured under its own conditions, so open its page before comparing closely. Compare every grade in the family.
| Measurement | h-BN | AlN | CrN | AlN-BN | Si3N4 | TiN | ZrN |
|---|---|---|---|---|---|---|---|
| Thermal behavior and safety | |||||||
| Thermal conductivity, Grade A, parallel to pressing | 30 W/(m·K)6 | 140 to 180 W/m•°K | no data | 92 W/mK | 24 W/mK | 26.96 W/(m·K) | no data |
| Thermal conductivity, Grade A, perpendicular to pressing | 34 W/(m·K)7 | 140 to 180 W/m•°K | no data | 92 W/mK | 24 W/mK | 26.96 W/(m·K) | no data |
| Thermal conductivity parallel to pressing, hot-pressed HP grade, lot 1 | 33 W/(m·K)17 | 140 to 180 W/m•°K | no data | 92 W/mK | 24 W/mK | 26.96 W/(m·K) | no data |
| Thermal conductivity perpendicular to pressing, hot-pressed HP grade, lot 1 | 31 W/(m·K)18 | 140 to 180 W/m•°K | no data | 92 W/mK | 24 W/mK | 26.96 W/(m·K) | no data |
| Thermal conductivity parallel to basal planes, h-BN material (not a grade) | 600 W/(m·K)32 | 140 to 180 W/m•°K | no data | 92 W/mK | 24 W/mK | 26.96 W/(m·K) | no data |
| Thermal conductivity perpendicular to basal planes, h-BN material (not a grade) | 30 W/(m·K)33 | 140 to 180 W/m•°K | no data | 92 W/mK | 24 W/mK | 26.96 W/(m·K) | no data |
| Physical and electrical | |||||||
| Density, hot-pressed boron nitride Grade A | 2 g/cm³1 | 3.26 gm/cc | 5.9 g/cm³ | 2.88 g/cm³ | 3.18 to 3.3 g/cm³ | no data | 7090 kg m-3 |
| Density, h-BN material (not a grade) | 2.1 g/cm³31 | 3.26 gm/cc | 5.9 g/cm³ | 2.88 g/cm³ | 3.18 to 3.3 g/cm³ | no data | 7090 kg m-3 |
| Temperature behavior | |||||||
| Temperature of first oxidation in ambient air, 20 min, h-BN single crystal | 900 °C34 | no data | no data | no data | no data | no data | no data |
| Other measurements | |||||||
| Flexural strength at 25 °C, Grade A, parallel to pressing | 94 MPa2 | 320 MPa | no data | 300 MPa | 670 MPa | no data | no data |
| Flexural strength at 25 °C, Grade A, perpendicular to pressing | 65 MPa3 | 320 MPa | no data | 300 MPa | 670 MPa | no data | no data |
| Young's modulus, Grade A, parallel to pressing | 47 GPa4 | 330 GPa | 200 GPa | 176 GPa | 290 GPa | 500 GPa | no data |
| Young's modulus, Grade A, perpendicular to pressing | 74 GPa5 | 330 GPa | 200 GPa | 176 GPa | 290 GPa | 500 GPa | no data |
| Coefficient of thermal expansion 25 to 400 °C, Grade A, parallel to pressing | 3 ppm/K8 | 4.5 10-6/°C | no data | 4.8 x10-6/°C | 3.2 10-6K-1 | no data | no data |
| Coefficient of thermal expansion 25 to 400 °C, Grade A, perpendicular to pressing | 3 ppm/K9 | 4.5 10-6/°C | no data | 4.8 x10-6/°C | 3.2 10-6K-1 | no data | no data |
| Coefficient of thermal expansion 400 to 800 °C, Grade A, parallel to pressing | 2 ppm/K10 | 4.5 10-6/°C | no data | 4.8 x10-6/°C | 3.2 10-6K-1 | no data | no data |
| Coefficient of thermal expansion 400 to 800 °C, Grade A, perpendicular to pressing | 1.4 ppm/K11 | 4.5 10-6/°C | no data | 4.8 x10-6/°C | 3.2 10-6K-1 | no data | no data |
| Maximum temperature in air, Grade A | 850 °C12 | no data | 700 °C | 1000 °C | 1200 °C | no data | no data |
| Maximum temperature in inert atmosphere, Grade A | 1200 °C13 | no data | 700 °C | 1000 °C | 1200 °C | no data | no data |
| Dielectric constant at 1 MHz, Grade A, parallel to pressing | 4.6 -14 | 9 - | no data | 6.8 - | no data | no data | no data |
| Dielectric constant at 1 MHz, Grade A, perpendicular to pressing | 4.2 -15 | 9 - | no data | 6.8 - | no data | no data | no data |
| Dielectric strength DC, Grade A | 88 kV/mm16 | 17 ac-kv/mm | no data | 65 kV/mm | no data | no data | no data |
| Coefficient of thermal expansion, hot-pressed HP grade, parallel to pressing | 3.1 ppm/K19 | 4.5 10-6/°C | no data | 4.8 x10-6/°C | 3.2 10-6K-1 | no data | no data |
| Coefficient of thermal expansion, hot-pressed HP grade, perpendicular to pressing | 0.4 ppm/K20 | 4.5 10-6/°C | no data | 4.8 x10-6/°C | 3.2 10-6K-1 | no data | no data |
| Elastic modulus, hot-pressed HP grade, parallel to pressing | 80 GPa21 | 330 GPa | 200 GPa | 176 GPa | 290 GPa | 500 GPa | no data |
| Elastic modulus, hot-pressed HP grade, perpendicular to pressing | 79 GPa22 | 330 GPa | 200 GPa | 176 GPa | 290 GPa | 500 GPa | no data |
| Dielectric constant, hot-pressed HP grade, parallel to pressing | 4.7 -23 | 9 - | no data | 6.8 - | no data | no data | no data |
| Flexural strength at 25 °C, hot-pressed HP grade, parallel to pressing | 39.7 MPa24 | 320 MPa | no data | 300 MPa | 670 MPa | no data | no data |
| Flexural strength at 25 °C, hot-pressed HP grade, perpendicular to pressing | 70.5 MPa25 | 320 MPa | no data | 300 MPa | 670 MPa | no data | no data |
| Flexural strength at 600 °C, hot-pressed HP grade, parallel to pressing | 9.8 MPa26 | 320 MPa | no data | 300 MPa | 670 MPa | no data | no data |
| Flexural strength at 600 °C, hot-pressed HP grade, perpendicular to pressing | 70.1 MPa27 | 320 MPa | no data | 300 MPa | 670 MPa | no data | no data |
| Weibull modulus of flexural strength at 25 °C, hot-pressed HP grade, parallel to pressing | 19.3 -28 | no data | no data | no data | 20 unitless | no data | no data |
| Weibull modulus of flexural strength at 25 °C, hot-pressed HP grade, perpendicular to pressing | 22.3 -29 | no data | no data | no data | 20 unitless | no data | no data |
| Porosity, hot-pressed HP grade | < 14 %30 | no data | no data | no data | no data | no data | no data |
Why choose it, and why not
Good for
- Electrical insulation at high temperature: 88 kV/mm dielectric strength in Grade A.
- Heat conduction in an insulator: 30 to 34 W/(m·K) in Grade A, and 600 W/(m·K) along the basal planes of h-BN.
- Lubrication up to 900 °C, including in vacuum.
Watch out for
- Hot strength: HP bending strength parallel to pressing is 9.8 MPa at 600 °C, against 39.7 MPa at 25 °C.
- Direction and lot: strength changes with pressing direction and between lots, and the trend reverses between grades.
- Oxidation: single crystals show pits in air from 900 °C after 20 minutes.
- Moisture: NASA reports moisture sensitivity of flexural strength and modulus, most in one lot.
- No erosion yield, outgassing or radiation value for hot-pressed h-BN was found in the sources read, so space-environment durability is not established here.
Hot-pressed h-BN is an insulator that resists thermal shock, with 88 kV/mm dielectric strength and an 850 °C air limit for Grade A. Its strength depends strongly on pressing direction, lot and temperature, and it oxidises in air from about 900 °C. NASA has tested grades for electric propulsion, but no space-environment erosion or outgassing number is in this profile.
Technical details
For scientists and researchers. Everything above comes from the record below: every number with its method, its conditions and its source.
Other names and standards
The same grade under other systems, as datasheets and standards print them. Each code was checked against the page it comes from.
| System | Codes |
|---|---|
| Trade name | Grade A, HP, AX05, PT110 |
Notes
The method, full conditions and any caveat for the numbered rows above.
| # | Measurement | Method | Conditions | Caveat |
|---|---|---|---|---|
| 1 | Density, hot-pressed boron nitride Grade A | Mean and typical value printed in a manufacturer material datasheet, with the datasheet disclaimer that values are indicative | grade Grade A (Precision Ceramics UK)form hot-pressedtemperature not statedunit in source g/cm3 | — |
| 2 | Flexural strength at 25 °C, Grade A, parallel to pressing | Mean and typical value printed in a manufacturer material datasheet | grade Grade A (Precision Ceramics UK)temperature 25 °Cdirection parallel to hot-press directionform hot-pressed | — |
| 3 | Flexural strength at 25 °C, Grade A, perpendicular to pressing | Mean and typical value printed in a manufacturer material datasheet | grade Grade A (Precision Ceramics UK)temperature 25 °Cdirection perpendicular to hot-press directionform hot-pressed | — |
| 4 | Young's modulus, Grade A, parallel to pressing | Value printed in a manufacturer material datasheet | grade Grade A (Precision Ceramics UK)direction parallel to hot-press directiontemperature not stated | — |
| 5 | Young's modulus, Grade A, perpendicular to pressing | Value printed in a manufacturer material datasheet | grade Grade A (Precision Ceramics UK)direction perpendicular to hot-press directiontemperature not stated | — |
| 6 | Thermal conductivity, Grade A, parallel to pressing | Value printed in a manufacturer material datasheet | grade Grade A (Precision Ceramics UK)direction parallel to hot-press directiontemperature not statedunit in source W/mK | — |
| 7 | Thermal conductivity, Grade A, perpendicular to pressing | Value printed in a manufacturer material datasheet | grade Grade A (Precision Ceramics UK)direction perpendicular to hot-press directiontemperature not statedunit in source W/mK | — |
| 8 | Coefficient of thermal expansion 25 to 400 °C, Grade A, parallel to pressing | Value printed in a manufacturer material datasheet | grade Grade A (Precision Ceramics UK)temperature range 25 to 400 °Cdirection parallel to hot-press directionunit in source 10^-6/K | — |
| 9 | Coefficient of thermal expansion 25 to 400 °C, Grade A, perpendicular to pressing | Value printed in a manufacturer material datasheet | grade Grade A (Precision Ceramics UK)temperature range 25 to 400 °Cdirection perpendicular to hot-press directionunit in source 10^-6/K | — |
| 10 | Coefficient of thermal expansion 400 to 800 °C, Grade A, parallel to pressing | Value printed in a manufacturer material datasheet | grade Grade A (Precision Ceramics UK)temperature range 400 to 800 °Cdirection parallel to hot-press directionunit in source 10^-6/K | — |
| 11 | Coefficient of thermal expansion 400 to 800 °C, Grade A, perpendicular to pressing | Value printed in a manufacturer material datasheet | grade Grade A (Precision Ceramics UK)temperature range 400 to 800 °Cdirection perpendicular to hot-press directionunit in source 10^-6/K | — |
| 12 | Maximum temperature in air, Grade A | Maximum temperature printed in a manufacturer material datasheet; not a component design allowable | grade Grade A (Precision Ceramics UK)atmosphere air | — |
| 13 | Maximum temperature in inert atmosphere, Grade A | Maximum temperature printed in a manufacturer material datasheet; not a component design allowable | grade Grade A (Precision Ceramics UK)atmosphere inert | — |
| 14 | Dielectric constant at 1 MHz, Grade A, parallel to pressing | Value printed in a manufacturer material datasheet | grade Grade A (Precision Ceramics UK)frequency 1 MHzdirection parallel to hot-press direction | — |
| 15 | Dielectric constant at 1 MHz, Grade A, perpendicular to pressing | Value printed in a manufacturer material datasheet | grade Grade A (Precision Ceramics UK)frequency 1 MHzdirection perpendicular to hot-press direction | — |
| 16 | Dielectric strength DC, Grade A | Value printed in a manufacturer material datasheet | grade Grade A (Precision Ceramics UK)direction not statedcurrent DC | — |
| 17 | Thermal conductivity parallel to pressing, hot-pressed HP grade, lot 1 | Measured at NASA Glenn Research Center on a sample set of the HP grade and printed in a table | grade HP (Saint-Gobain BN with calcium borate binder)direction parallel to hot-press directionmethod in source ASTM E1461temperature not stated in the tableunit in source W/m-K | — |
| 18 | Thermal conductivity perpendicular to pressing, hot-pressed HP grade, lot 1 | Measured at NASA Glenn Research Center and printed in a table | grade HP (Saint-Gobain BN with calcium borate binder)direction perpendicular to hot-press directionmethod in source ASTM E1461temperature not stated in the tableunit in source W/m-K | — |
| 19 | Coefficient of thermal expansion, hot-pressed HP grade, parallel to pressing | Measured by dilatometry at NASA Glenn Research Center and printed in a table | grade HP (Saint-Gobain BN with calcium borate binder)direction parallel to hot-press directionmethod in source dilatometrytemperature not stated in the tableunit in source μm/m-K | — |
| 20 | Coefficient of thermal expansion, hot-pressed HP grade, perpendicular to pressing | Measured by dilatometry at NASA Glenn Research Center and printed in a table | grade HP (Saint-Gobain BN with calcium borate binder)direction perpendicular to hot-press directionmethod in source dilatometrytemperature not stated in the tableunit in source μm/m-K | — |
| 21 | Elastic modulus, hot-pressed HP grade, parallel to pressing | Measured at NASA Glenn Research Center and printed in a table | grade HP (Saint-Gobain BN with calcium borate binder)direction parallel to hot-press directionmethod in source ASTM C1259temperature not stated in the table | — |
| 22 | Elastic modulus, hot-pressed HP grade, perpendicular to pressing | Measured at NASA Glenn Research Center and printed in a table | grade HP (Saint-Gobain BN with calcium borate binder)direction perpendicular to hot-press directionmethod in source ASTM C1259temperature not stated in the table | — |
| 23 | Dielectric constant, hot-pressed HP grade, parallel to pressing | Measured at NASA Glenn Research Center and printed in a table | grade HP (Saint-Gobain BN with calcium borate binder)direction parallel to hot-press directionmethod in source impedance spectroscopytemperature not stated in the table | — |
| 24 | Flexural strength at 25 °C, hot-pressed HP grade, parallel to pressing | Average printed in a 4-point bend table at NASA Glenn Research Center | grade HP (Saint-Gobain BN with calcium borate binder)temperature 25 °Cdirection parallel to hot-press directiontest 4-point bendmeasure average of 26 or more samplessample state the slide lists as-machined and dry or humidity-chamber samples but the table does not separate themlot not printed on this slide; the first lot characterised | — |
| 25 | Flexural strength at 25 °C, hot-pressed HP grade, perpendicular to pressing | Average printed in a 4-point bend table at NASA Glenn Research Center | grade HP (Saint-Gobain BN with calcium borate binder)temperature 25 °Cdirection perpendicular to hot-press directiontest 4-point bendsample state the table does not separate as-machined, dry or humidity-chamber sampleslot not printed on this slide; the first lot characterised | — |
| 26 | Flexural strength at 600 °C, hot-pressed HP grade, parallel to pressing | Average printed in a 4-point bend table at NASA Glenn Research Center | grade HP (Saint-Gobain BN with calcium borate binder)temperature 600 °Cdirection parallel to hot-press directiontest 4-point bendlot not printed on this slide; the first lot characterised | — |
| 27 | Flexural strength at 600 °C, hot-pressed HP grade, perpendicular to pressing | Average printed in a 4-point bend table at NASA Glenn Research Center | grade HP (Saint-Gobain BN with calcium borate binder)temperature 600 °Cdirection perpendicular to hot-press directiontest 4-point bendlot not printed on this slide; the first lot characterised | — |
| 28 | Weibull modulus of flexural strength at 25 °C, hot-pressed HP grade, parallel to pressing | Printed Weibull modulus from a 4-point bend table at NASA Glenn Research Center; name not in the canonical property file | grade HP (Saint-Gobain BN with calcium borate binder)temperature 25 °Cdirection parallel to hot-press direction | — |
| 29 | Weibull modulus of flexural strength at 25 °C, hot-pressed HP grade, perpendicular to pressing | Printed Weibull modulus from a 4-point bend table at NASA Glenn Research Center; name not in the canonical property file | grade HP (Saint-Gobain BN with calcium borate binder)temperature 25 °Cdirection perpendicular to hot-press direction | — |
| 30 | Porosity, hot-pressed HP grade | Upper bound printed in a table at NASA Glenn Research Center; name not in the canonical property file | grade HP (Saint-Gobain BN with calcium borate binder)printed value <14method in source ASTM C830 | — |
| 31 | Density, h-BN material (not a grade) | Value in the Properties infobox of the Wikipedia article on boron nitride | form hexagonal BN, material-level value, not a gradetemperature not statedunit in source 2.1 g/cm3 (h-BN) | — |
| 32 | Thermal conductivity parallel to basal planes, h-BN material (not a grade) | Value printed in the Physical properties table of the Wikipedia article on boron nitride, in the h-BN row | form hexagonal BN, material-level value, parallel to the basal planestemperature not stated | — |
| 33 | Thermal conductivity perpendicular to basal planes, h-BN material (not a grade) | Value printed in the Physical properties table of the Wikipedia article on boron nitride, in the h-BN row | form hexagonal BN, material-level value, perpendicular to the basal planestemperature not stated | — |
| 34 | Temperature of first oxidation in ambient air, 20 min, h-BN single crystal | Abstract of an AFM and SEM/EDS study; name not in the canonical property file. The value is a first sign of oxidation, not a service limit | form (0001) h-BN single crystal, not a hot-pressed gradeatmosphere ambient airexposure 20 minutesdetection AFM and SEM/EDS | — |
Corrosion and compatibility
What happens when it meets other materials and environments.
| Environment | Concern | What happens |
|---|---|---|
| Ambient air at high temperature | moderate | Oxidation of h-BN in air first shows at about 900 °C after 20 minutes, as shallow pits.1 |
| Water vapour and humidity | moderate | Strength and elastic modulus of hot-pressed h-BN are moisture sensitive, and the sensitivity differs between lots.2 |
| Electric propulsion plasma and back-sputtered deposition | not rated | Plasma erosion and back-sputtered deposition are the tested failure modes for electric propulsion; no erosion rate was found.3 |
| # | Environment | Details | Test conditions |
|---|---|---|---|
| 1 | Ambient air at high temperature | On (0001) single crystals in ambient air, the first evidence of oxidation was shallow hexagonal pits under 100 nm across and several nanometres deep at 900 °C for 20 minutes. At 1100 °C for 20 minutes the pits reached 1.0 to 2.0 µm, and the surface formed boron and oxygen particles. | form (0001) h-BN single crystal, not a hot-pressed gradeatmosphere ambient airexposure 20 minutes at each temperature |
| 2 | Water vapour and humidity | NASA lists flexural strength and elastic modulus among the properties with significant lot-to-lot variation, and says Lot 2 is more moisture sensitive. The moisture absorption and density show minimal lot-to-lot variation. The moisture-soak strength numbers are in the slides but are not used as values in this profile. | grades HP, M26, M (Saint-Gobain)test soak in a humidity chamber and submerged in water at 25 °C, then 4-point bend |
| 3 | Electric propulsion plasma and back-sputtered deposition | NASA lists plasma erosion, high temperature, low temperature, vacuum and back-sputtered deposition as harsh conditions that electric propulsion ceramics may face. The sources read give no erosion rate or secondary electron yield value for hot-pressed h-BN. | environment electric propulsion, plasmaerosion rate not found in the sources read |
Risks and side effects
Hazards to people, what happens when a cell overheats, and how the material is handled and stored.
For people
The classification depends on who notified it, and the sources do not give exposure limits.
- Boron nitride as a substance
- Of 480 company reports to the European chemicals agency, 422 say it does not meet GHS criteria. Among those that gave codes, H319 (serious eye irritation, 11.7 %) and H335 (respiratory irritation, 10.8 %) are the most common.
- Cosmetic use
- The cosmetic review summarised by PubChem finds it safe in present practices of use and concentration.
If it fails
These failures are from the sources read. The bending data are measured at NASA, the oxidation data are from a single crystal study.
- Hot strength
- HP bending strength parallel to pressing falls from 39.7 MPa at 25 °C to 9.8 MPa at 600 °C.
- Air
- In ambient air, single h-BN crystals first show oxidation pits at 900 °C after 20 minutes.
- Lot change
- NASA finds that flexural strength and elastic modulus vary significantly between lots, so a grade name alone does not fix the strength.
Handling and storage
- Specify direction and lot
- Strength differs parallel and perpendicular to pressing, and between lots. Name the grade, the pressing direction and the lot.
- Temperature
- Grade A is rated to 850 °C in air and 1200 °C in inert atmosphere.
Test details
The original wording and numbers from the sources, for readers who want them.
Failure risks
| Failure | Trigger and consequence |
|---|---|
| Bending failure at high temperature, parallel to pressinghigh severity | Load applied parallel to the hot-press direction of the HP grade at 600 °CAverage bending strength falls from 39.7 MPa at 25 °C to 9.8 MPa at 600 °C. NASA also notes significant deflection of HP at 600 °C, and suggests a CaF2 or calcium borate related mechanism. |
| Strength depends on hot-press orientationmoderate severity | Part orientation relative to the hot-press axis is not controlledHP bending strength is 39.7 MPa parallel and 70.5 MPa perpendicular at 25 °C, while Grade A gives 94 MPa parallel and 65 MPa perpendicular. The grades reverse the trend, so one orientation rule cannot be assumed. |
| Brittle failure at room temperaturemoderate severity | Loading of any tested grade at room temperatureNASA reports that all grades tested, HP, M and M26, failed in a brittle manner at 25 °C, so no yield or plastic warning should be assumed. |
| Oxidation pitting in airmoderate severity | Sustained exposure in ambient air near or above 900 °CShallow pits form first; at 1100 °C for 20 minutes they are 1 to 2 µm across. The effect on strength is not measured in the sources read. |
| Lot-to-lot variationmoderate severity | Change of production lotNASA finds significant lot-to-lot variation in flexural strength and elastic modulus, and says only two lots have been characterised so far. |
Handling and storage
- Specify the grade, the hot-press direction and the lot number, because strength and modulus change with direction and lot.
- Keep the part below 850 °C in air for Grade A; the 1200 °C figure is for an inert atmosphere only.
- Limit dust. PubChem lists precautionary codes P261 (avoid breathing dust), P271 (use outdoors or in a well-ventilated area) and P280 (wear protective equipment) among the codes reported for boron nitride.
Supply and geography
How common the raw materials are and where they come from.
Boron feedstock for h-BN (borates)
USGS 2026: Turkey produced 1,500 thousand metric tons of refined borates in 2025 (1,800 in 2024) and holds reserves of 950,000 thousand metric tons, the largest in the table. The United States reports reserves of 48,000 thousand metric tons. Turkey supplied 90 % of U.S. boron imports in 2021 to 2024.
- Critical mineral lists
- U.S. Final 2025 List of Critical Minerals (boron added in 2025): listed
Producers named for hot-pressed h-BN grades in the sources read
NASA 2020 lists Saint-Gobain (HP, M26, M), Kennametal (BN-XX) and Tokuyama or Precision Ceramics (Hi-M). Precision Ceramics UK sells Grade A. NASA 2017 used Momentive PT110 powder as the h-BN starting material. Stanford Advanced Materials is a distributor of hot-pressed BN.
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spore: profile
id: boron-nitride
spore_version: 0.2
family: carbide-nitride-boride-ceramics
name: Hexagonal boron nitride
abbreviation: h-BN
role: electrical insulator and thermal ceramic
category: ceramics
type: nitrides
summary: |
Hexagonal boron nitride (h-BN) is a graphite-like layered form of BN. Hot-pressed ceramic grades are electrically insulating and resist thermal shock. Precision Ceramics Grade A has a bending strength of 94 MPa parallel to the pressing direction and 65 MPa perpendicular to it, a dielectric strength of 88 kV/mm, and is rated to 850 °C in air. Its thermal conductivity is only 30 to 34 W/(m·K), far below the 600 W/(m·K) quoted for the basal planes of the h-BN material, and NASA measured bending strength falling from 39.7 MPa to 9.8 MPa at 600 °C in one hot-pressed grade.
best_for: Electrical insulation and microwave or high-temperature insulating parts, where the 88 kV/mm dielectric strength and the 850 °C air limit of Grade A matter
weakest_at: 'Strength across or at high temperature: HP bending strength parallel to pressing falls from 39.7 MPa at 25 °C to 9.8 MPa at 600 °C, and oxidation in ambient air begins near 900 °C'
identity:
formula: 'BN, hexagonal boron nitride (one boron and one nitrogen atom per formula unit, bonded in graphite-like layers). Hot-pressed grades contain a binder: calcium borate in NASA''s HP grade, B2O3 in the SAM BN-BO Grade A'
cas: 10043-11-5
source: pubchem-bn
where: Molecular Formula BN and the CAS number 10043-11-5 in the Identifiers section, CID 66227
designations:
- system: Trade name
code: Grade A
note: Precision Ceramics name for its hot-pressed h-BN grade, Mean and typical values
source: pc-uk-grade-a
where: Title line of the material datasheet
- system: Trade name
code: HP
note: Saint-Gobain hot-pressed h-BN grade with calcium borate binder
source: nasa-2020-bn
where: Materials of Interest table, Grade column
- system: Trade name
code: AX05
note: h-BN above 99.5 %, self-bonded, as listed by Stanford Advanced Materials
source: sam-bn-hp
where: Hot Pressed Boron Nitride Crucible specification table, column BN99 (Grade AX05)
- system: Trade name
code: PT110
note: Momentive powder used as the h-BN starting material for hot-pressed composites, not a dense ceramic
source: nasa-2017-hbn
where: Experimental section, paragraph on the h-BN material
tags:
environments: []
stresses:
- extreme-heat
applications:
- propulsion-and-tanks
- electronics-and-chips
- mechanisms
properties:
- benchmark: density
label: Density, hot-pressed boron nitride Grade A
value: 2
unit: g/cm3
scope: material
conditions:
grade: Grade A (Precision Ceramics UK)
form: hot-pressed
temperature: not stated
unit_in_source: g/cm3
method: Mean and typical value printed in a manufacturer material datasheet, with the datasheet disclaimer that values are indicative
status: ground
source: pc-uk-grade-a
where: Material datasheet, Mechanical block, row Density
- benchmark: flexural_strength
label: Flexural strength at 25 °C, Grade A, parallel to pressing
value: 94
unit: MPa
scope: material
conditions:
grade: Grade A (Precision Ceramics UK)
temperature: 25 °C
direction: parallel to hot-press direction
form: hot-pressed
method: Mean and typical value printed in a manufacturer material datasheet
status: ground
source: pc-uk-grade-a
where: Material datasheet, Mechanical block, row Flexural Strength at 25 °C, column 94 parallel
- benchmark: flexural_strength
label: Flexural strength at 25 °C, Grade A, perpendicular to pressing
value: 65
unit: MPa
scope: material
conditions:
grade: Grade A (Precision Ceramics UK)
temperature: 25 °C
direction: perpendicular to hot-press direction
form: hot-pressed
method: Mean and typical value printed in a manufacturer material datasheet
status: ground
source: pc-uk-grade-a
where: Material datasheet, Mechanical block, row Flexural Strength at 25 °C, column 65 perpendicular
- benchmark: elastic_modulus
label: Young's modulus, Grade A, parallel to pressing
value: 47
unit: GPa
scope: material
conditions:
grade: Grade A (Precision Ceramics UK)
direction: parallel to hot-press direction
temperature: not stated
method: Value printed in a manufacturer material datasheet
status: ground
source: pc-uk-grade-a
where: Material datasheet, Mechanical block, row Young's Modulus
- benchmark: elastic_modulus
label: Young's modulus, Grade A, perpendicular to pressing
value: 74
unit: GPa
scope: material
conditions:
grade: Grade A (Precision Ceramics UK)
direction: perpendicular to hot-press direction
temperature: not stated
method: Value printed in a manufacturer material datasheet
status: ground
source: pc-uk-grade-a
where: Material datasheet, Mechanical block, row Young's Modulus
- benchmark: thermal_conductivity
label: Thermal conductivity, Grade A, parallel to pressing
value: 30
unit: W/(m·K)
scope: material
conditions:
grade: Grade A (Precision Ceramics UK)
direction: parallel to hot-press direction
temperature: not stated
unit_in_source: W/mK
method: Value printed in a manufacturer material datasheet
status: ground
source: pc-uk-grade-a
where: Material datasheet, Thermal block, row Thermal Conductivity, column 30 parallel
- benchmark: thermal_conductivity
label: Thermal conductivity, Grade A, perpendicular to pressing
value: 34
unit: W/(m·K)
scope: material
conditions:
grade: Grade A (Precision Ceramics UK)
direction: perpendicular to hot-press direction
temperature: not stated
unit_in_source: W/mK
method: Value printed in a manufacturer material datasheet
status: ground
source: pc-uk-grade-a
where: Material datasheet, Thermal block, row Thermal Conductivity, column 34 perpendicular
- benchmark: cte
label: Coefficient of thermal expansion 25 to 400 °C, Grade A, parallel to pressing
value: 3
unit: ppm/K
scope: material
conditions:
grade: Grade A (Precision Ceramics UK)
temperature_range: 25 to 400 °C
direction: parallel to hot-press direction
unit_in_source: 10^-6/K
method: Value printed in a manufacturer material datasheet
status: ground
source: pc-uk-grade-a
where: Material datasheet, Thermal block, row CTE at 25 to 400 °C
- benchmark: cte
label: Coefficient of thermal expansion 25 to 400 °C, Grade A, perpendicular to pressing
value: 3
unit: ppm/K
scope: material
conditions:
grade: Grade A (Precision Ceramics UK)
temperature_range: 25 to 400 °C
direction: perpendicular to hot-press direction
unit_in_source: 10^-6/K
method: Value printed in a manufacturer material datasheet
status: ground
source: pc-uk-grade-a
where: Material datasheet, Thermal block, row CTE at 25 to 400 °C
- benchmark: cte
label: Coefficient of thermal expansion 400 to 800 °C, Grade A, parallel to pressing
value: 2
unit: ppm/K
scope: material
conditions:
grade: Grade A (Precision Ceramics UK)
temperature_range: 400 to 800 °C
direction: parallel to hot-press direction
unit_in_source: 10^-6/K
method: Value printed in a manufacturer material datasheet
status: ground
source: pc-uk-grade-a
where: Material datasheet, Thermal block, row CTE at 400 to 800 °C
- benchmark: cte
label: Coefficient of thermal expansion 400 to 800 °C, Grade A, perpendicular to pressing
value: 1.4
unit: ppm/K
scope: material
conditions:
grade: Grade A (Precision Ceramics UK)
temperature_range: 400 to 800 °C
direction: perpendicular to hot-press direction
unit_in_source: 10^-6/K
method: Value printed in a manufacturer material datasheet
status: ground
source: pc-uk-grade-a
where: Material datasheet, Thermal block, row CTE at 400 to 800 °C
- benchmark: max_service_temp
label: Maximum temperature in air, Grade A
value: 850
unit: °C
scope: material
conditions:
grade: Grade A (Precision Ceramics UK)
atmosphere: air
method: Maximum temperature printed in a manufacturer material datasheet; not a component design allowable
status: ground
source: pc-uk-grade-a
where: Material datasheet, Thermal block, row Maximum Temperature (Air)
- benchmark: max_service_temp
label: Maximum temperature in inert atmosphere, Grade A
value: 1200
unit: °C
scope: material
conditions:
grade: Grade A (Precision Ceramics UK)
atmosphere: inert
method: Maximum temperature printed in a manufacturer material datasheet; not a component design allowable
status: ground
source: pc-uk-grade-a
where: Material datasheet, Thermal block, row Maximum Temperature (Inert)
- benchmark: dielectric_constant
label: Dielectric constant at 1 MHz, Grade A, parallel to pressing
value: 4.6
unit: '-'
scope: material
conditions:
grade: Grade A (Precision Ceramics UK)
frequency: 1 MHz
direction: parallel to hot-press direction
method: Value printed in a manufacturer material datasheet
status: ground
source: pc-uk-grade-a
where: Material datasheet, Electrical block, row Dielectric Constant at 1 MHz, column 4.6 parallel
- benchmark: dielectric_constant
label: Dielectric constant at 1 MHz, Grade A, perpendicular to pressing
value: 4.2
unit: '-'
scope: material
conditions:
grade: Grade A (Precision Ceramics UK)
frequency: 1 MHz
direction: perpendicular to hot-press direction
method: Value printed in a manufacturer material datasheet
status: ground
source: pc-uk-grade-a
where: Material datasheet, Electrical block, row Dielectric Constant at 1 MHz, column 4.2 perpendicular
- benchmark: dielectric_strength
label: Dielectric strength DC, Grade A
value: 88
unit: kV/mm
scope: material
conditions:
grade: Grade A (Precision Ceramics UK)
direction: not stated
current: DC
method: Value printed in a manufacturer material datasheet
status: ground
source: pc-uk-grade-a
where: Material datasheet, Electrical block, row Dielectric Strength DC
- benchmark: thermal_conductivity
label: Thermal conductivity parallel to pressing, hot-pressed HP grade, lot 1
value: 33
unit: W/(m·K)
scope: material
conditions:
grade: HP (Saint-Gobain BN with calcium borate binder)
direction: parallel to hot-press direction
method_in_source: ASTM E1461
temperature: not stated in the table
unit_in_source: W/m-K
method: Measured at NASA Glenn Research Center on a sample set of the HP grade and printed in a table
status: ground
source: nasa-2020-bn
where: General Properties Overview (cont.), table Property trends in BN/SiO2 content, row Thermal Conductivity, column HP parallel
- benchmark: thermal_conductivity
label: Thermal conductivity perpendicular to pressing, hot-pressed HP grade, lot 1
value: 31
unit: W/(m·K)
scope: material
conditions:
grade: HP (Saint-Gobain BN with calcium borate binder)
direction: perpendicular to hot-press direction
method_in_source: ASTM E1461
temperature: not stated in the table
unit_in_source: W/m-K
method: Measured at NASA Glenn Research Center and printed in a table
status: ground
source: nasa-2020-bn
where: General Properties Overview (cont.), table Property trends in BN/SiO2 content, row Thermal Conductivity, column HP perpendicular
- benchmark: cte
label: Coefficient of thermal expansion, hot-pressed HP grade, parallel to pressing
value: 3.1
unit: ppm/K
scope: material
conditions:
grade: HP (Saint-Gobain BN with calcium borate binder)
direction: parallel to hot-press direction
method_in_source: dilatometry
temperature: not stated in the table
unit_in_source: μm/m-K
method: Measured by dilatometry at NASA Glenn Research Center and printed in a table
status: ground
source: nasa-2020-bn
where: General Properties Overview (cont.), table Property trends in BN/SiO2 content, row CTE, column HP parallel
- benchmark: cte
label: Coefficient of thermal expansion, hot-pressed HP grade, perpendicular to pressing
value: 0.4
unit: ppm/K
scope: material
conditions:
grade: HP (Saint-Gobain BN with calcium borate binder)
direction: perpendicular to hot-press direction
method_in_source: dilatometry
temperature: not stated in the table
unit_in_source: μm/m-K
method: Measured by dilatometry at NASA Glenn Research Center and printed in a table
status: ground
source: nasa-2020-bn
where: General Properties Overview (cont.), table Property trends in BN/SiO2 content, row CTE, column HP perpendicular
- benchmark: elastic_modulus
label: Elastic modulus, hot-pressed HP grade, parallel to pressing
value: 80
unit: GPa
scope: material
conditions:
grade: HP (Saint-Gobain BN with calcium borate binder)
direction: parallel to hot-press direction
method_in_source: ASTM C1259
temperature: not stated in the table
method: Measured at NASA Glenn Research Center and printed in a table
status: ground
source: nasa-2020-bn
where: General Properties Overview (cont.), table Property trends in BN/SiO2 content, row Elastic Modulus, column HP parallel
- benchmark: elastic_modulus
label: Elastic modulus, hot-pressed HP grade, perpendicular to pressing
value: 79
unit: GPa
scope: material
conditions:
grade: HP (Saint-Gobain BN with calcium borate binder)
direction: perpendicular to hot-press direction
method_in_source: ASTM C1259
temperature: not stated in the table
method: Measured at NASA Glenn Research Center and printed in a table
status: ground
source: nasa-2020-bn
where: General Properties Overview (cont.), table Property trends in BN/SiO2 content, row Elastic Modulus, column HP perpendicular
- benchmark: dielectric_constant
label: Dielectric constant, hot-pressed HP grade, parallel to pressing
value: 4.7
unit: '-'
scope: material
conditions:
grade: HP (Saint-Gobain BN with calcium borate binder)
direction: parallel to hot-press direction
method_in_source: impedance spectroscopy
temperature: not stated in the table
method: Measured at NASA Glenn Research Center and printed in a table
status: ground
source: nasa-2020-bn
where: General Properties Overview (cont.), table Property trends in BN/SiO2 content, row Dielectric Constant, column HP parallel
- benchmark: flexural_strength
label: Flexural strength at 25 °C, hot-pressed HP grade, parallel to pressing
value: 39.7
unit: MPa
scope: material
conditions:
grade: HP (Saint-Gobain BN with calcium borate binder)
temperature: 25 °C
direction: parallel to hot-press direction
test: 4-point bend
measure: average of 26 or more samples
sample_state: the slide lists as-machined and dry or humidity-chamber samples but the table does not separate them
lot: not printed on this slide; the first lot characterised
method: Average printed in a 4-point bend table at NASA Glenn Research Center
status: ground
source: nasa-2020-bn
where: Flexural Testing (cont.) table, row HP parallel, column Average at room temperature
- benchmark: flexural_strength
label: Flexural strength at 25 °C, hot-pressed HP grade, perpendicular to pressing
value: 70.5
unit: MPa
scope: material
conditions:
grade: HP (Saint-Gobain BN with calcium borate binder)
temperature: 25 °C
direction: perpendicular to hot-press direction
test: 4-point bend
sample_state: the table does not separate as-machined, dry or humidity-chamber samples
lot: not printed on this slide; the first lot characterised
method: Average printed in a 4-point bend table at NASA Glenn Research Center
status: ground
source: nasa-2020-bn
where: Flexural Testing (cont.) table, row HP perpendicular, column Average at room temperature
- benchmark: flexural_strength
label: Flexural strength at 600 °C, hot-pressed HP grade, parallel to pressing
value: 9.8
unit: MPa
scope: material
conditions:
grade: HP (Saint-Gobain BN with calcium borate binder)
temperature: 600 °C
direction: parallel to hot-press direction
test: 4-point bend
lot: not printed on this slide; the first lot characterised
method: Average printed in a 4-point bend table at NASA Glenn Research Center
status: ground
source: nasa-2020-bn
where: Flexural Testing (cont.) table, row HP parallel, column Average at 600 C
- benchmark: flexural_strength
label: Flexural strength at 600 °C, hot-pressed HP grade, perpendicular to pressing
value: 70.1
unit: MPa
scope: material
conditions:
grade: HP (Saint-Gobain BN with calcium borate binder)
temperature: 600 °C
direction: perpendicular to hot-press direction
test: 4-point bend
lot: not printed on this slide; the first lot characterised
method: Average printed in a 4-point bend table at NASA Glenn Research Center
status: ground
source: nasa-2020-bn
where: Flexural Testing (cont.) table, row HP perpendicular, column Average at 600 C
- benchmark: weibull_modulus
label: Weibull modulus of flexural strength at 25 °C, hot-pressed HP grade, parallel to pressing
value: 19.3
unit: '-'
scope: material
conditions:
grade: HP (Saint-Gobain BN with calcium borate binder)
temperature: 25 °C
direction: parallel to hot-press direction
method: Printed Weibull modulus from a 4-point bend table at NASA Glenn Research Center; name not in the canonical property file
status: ground
source: nasa-2020-bn
where: Flexural Testing (cont.) table, row HP parallel, column Weibull Modulus at room temperature
- benchmark: weibull_modulus
label: Weibull modulus of flexural strength at 25 °C, hot-pressed HP grade, perpendicular to pressing
value: 22.3
unit: '-'
scope: material
conditions:
grade: HP (Saint-Gobain BN with calcium borate binder)
temperature: 25 °C
direction: perpendicular to hot-press direction
method: Printed Weibull modulus from a 4-point bend table at NASA Glenn Research Center; name not in the canonical property file
status: ground
source: nasa-2020-bn
where: Flexural Testing (cont.) table, row HP perpendicular, column Weibull Modulus at room temperature
- benchmark: porosity
label: Porosity, hot-pressed HP grade
value: 14
bound: upper
unit: '%'
scope: material
conditions:
grade: HP (Saint-Gobain BN with calcium borate binder)
printed_value: <14
method_in_source: ASTM C830
method: Upper bound printed in a table at NASA Glenn Research Center; name not in the canonical property file
status: ground
source: nasa-2020-bn
where: General Properties Overview (cont.), table Property trends in BN/SiO2 content, row Porosity, column HP
- benchmark: density
label: Density, h-BN material (not a grade)
value: 2.1
unit: g/cm3
scope: material
conditions:
form: hexagonal BN, material-level value, not a grade
temperature: not stated
unit_in_source: 2.1 g/cm3 (h-BN)
method: Value in the Properties infobox of the Wikipedia article on boron nitride
status: ground
source: wiki-bn
where: Infobox, Properties, Density row, h-BN value
- benchmark: thermal_conductivity
label: Thermal conductivity parallel to basal planes, h-BN material (not a grade)
value: 600
unit: W/(m·K)
scope: material
conditions:
form: hexagonal BN, material-level value, parallel to the basal planes
temperature: not stated
method: Value printed in the Physical properties table of the Wikipedia article on boron nitride, in the h-BN row
status: ground
source: wiki-bn
where: Properties, Physical, thermal conductivity table, h-BN row, parallel value
- benchmark: thermal_conductivity
label: Thermal conductivity perpendicular to basal planes, h-BN material (not a grade)
value: 30
unit: W/(m·K)
scope: material
conditions:
form: hexagonal BN, material-level value, perpendicular to the basal planes
temperature: not stated
method: Value printed in the Physical properties table of the Wikipedia article on boron nitride, in the h-BN row
status: ground
source: wiki-bn
where: Properties, Physical, thermal conductivity table, h-BN row, perpendicular value
- benchmark: first_oxidation_temperature
label: Temperature of first oxidation in ambient air, 20 min, h-BN single crystal
value: 900
unit: °C
scope: material
conditions:
form: (0001) h-BN single crystal, not a hot-pressed grade
atmosphere: ambient air
exposure: 20 minutes
detection: AFM and SEM/EDS
method: Abstract of an AFM and SEM/EDS study; name not in the canonical property file. The value is a first sign of oxidation, not a service limit
status: ground
source: khan2019-hbn-oxidation
where: Abstract, first sentence on oxidation at 900 C for 20 minutes
corrosion:
- environment: Ambient air at high temperature
headline: Oxidation of h-BN in air first shows at about 900 °C after 20 minutes, as shallow pits.
effect: On (0001) single crystals in ambient air, the first evidence of oxidation was shallow hexagonal pits under 100 nm across and several nanometres deep at 900 °C for 20 minutes. At 1100 °C for 20 minutes the pits reached 1.0 to 2.0 µm, and the surface formed boron and oxygen particles.
rating: moderate
conditions:
form: (0001) h-BN single crystal, not a hot-pressed grade
atmosphere: ambient air
exposure: 20 minutes at each temperature
source: khan2019-hbn-oxidation
where: Abstract
- environment: Water vapour and humidity
headline: Strength and elastic modulus of hot-pressed h-BN are moisture sensitive, and the sensitivity differs between lots.
effect: NASA lists flexural strength and elastic modulus among the properties with significant lot-to-lot variation, and says Lot 2 is more moisture sensitive. The moisture absorption and density show minimal lot-to-lot variation. The moisture-soak strength numbers are in the slides but are not used as values in this profile.
rating: moderate
conditions:
grades: HP, M26, M (Saint-Gobain)
test: soak in a humidity chamber and submerged in water at 25 °C, then 4-point bend
source: nasa-2020-bn
where: Moisture Sensitivity slides and Summary slide
- environment: Electric propulsion plasma and back-sputtered deposition
headline: Plasma erosion and back-sputtered deposition are the tested failure modes for electric propulsion; no erosion rate was found.
effect: NASA lists plasma erosion, high temperature, low temperature, vacuum and back-sputtered deposition as harsh conditions that electric propulsion ceramics may face. The sources read give no erosion rate or secondary electron yield value for hot-pressed h-BN.
rating: unknown
conditions:
environment: electric propulsion, plasma
erosion_rate: not found in the sources read
source: nasa-2020-bn
where: Introduction, Electric Propulsion slide and Factors of Interest slide
risks:
hazards:
- text: PubChem aggregates ECHA C&L notifications for boron nitride. Of 480 company reports, 422 (87.9 %) say the substance does not meet GHS criteria. Of the reports that give codes, 11.7 % list H319 (causes serious eye irritation) and 10.8 % list H335 (may cause respiratory irritation). Signal word Warning. The record notes that the classification varies with impurities and additives.
ghs:
- H319
- H335
source: pubchem-bn
where: 9.1.1 GHS Classification, ECHA C&L Notifications Summary
- text: PubChem summarises the cosmetic review of boron nitride (CIR, 2015) as safe in the present practices of use and concentration. This is a cosmetic use conclusion, not a workplace limit.
ghs: []
source: pubchem-bn
where: 10.1.1 Toxicity Summary, Cosmetic Ingredient Review Finding
failure_risks:
- mode: Bending failure at high temperature, parallel to pressing
trigger: Load applied parallel to the hot-press direction of the HP grade at 600 °C
consequence: Average bending strength falls from 39.7 MPa at 25 °C to 9.8 MPa at 600 °C. NASA also notes significant deflection of HP at 600 °C, and suggests a CaF2 or calcium borate related mechanism.
severity: high
source: nasa-2020-bn
where: Flexural Testing slides, HP parallel row
- mode: Strength depends on hot-press orientation
trigger: Part orientation relative to the hot-press axis is not controlled
consequence: HP bending strength is 39.7 MPa parallel and 70.5 MPa perpendicular at 25 °C, while Grade A gives 94 MPa parallel and 65 MPa perpendicular. The grades reverse the trend, so one orientation rule cannot be assumed.
severity: moderate
source: pc-uk-grade-a
where: Material datasheet, Mechanical block, Flexural Strength row
- mode: Brittle failure at room temperature
trigger: Loading of any tested grade at room temperature
consequence: NASA reports that all grades tested, HP, M and M26, failed in a brittle manner at 25 °C, so no yield or plastic warning should be assumed.
severity: moderate
source: nasa-2020-bn
where: Flexural Testing slide
- mode: Oxidation pitting in air
trigger: Sustained exposure in ambient air near or above 900 °C
consequence: Shallow pits form first; at 1100 °C for 20 minutes they are 1 to 2 µm across. The effect on strength is not measured in the sources read.
severity: moderate
source: khan2019-hbn-oxidation
where: Abstract
- mode: Lot-to-lot variation
trigger: Change of production lot
consequence: NASA finds significant lot-to-lot variation in flexural strength and elastic modulus, and says only two lots have been characterised so far.
severity: moderate
source: nasa-2020-bn
where: Summary slide
side_effects: []
handling:
- text: Specify the grade, the hot-press direction and the lot number, because strength and modulus change with direction and lot.
source: nasa-2020-bn
where: General Properties Overview, Hot Press Direction slide, and Summary slide
- text: Keep the part below 850 °C in air for Grade A; the 1200 °C figure is for an inert atmosphere only.
source: pc-uk-grade-a
where: Material datasheet, Thermal block, Maximum Temperature rows
- text: Limit dust. PubChem lists precautionary codes P261 (avoid breathing dust), P271 (use outdoors or in a well-ventilated area) and P280 (wear protective equipment) among the codes reported for boron nitride.
source: pubchem-bn
where: 9.1.1 GHS Classification, Precautionary Statement Codes
mitigations: []
uses:
- application: propulsion-and-tanks
device: Insulators and components in space electric propulsion
example: NASA Glenn and JPL tested commercially available hot-pressed h-BN grades for space electric propulsion, where components must provide electrical isolation, thermal isolation or limited structural support. The report tests grades for lot-to-lot consistency; it does not state which grade flew.
source: nasa-2020-bn
where: Title, Introduction and Materials of Interest slides
- application: electronics-and-chips
device: High-voltage electrical insulator with high thermal conductivity
example: NASA Glenn describes an exfoliated h-BN and alumina ceramic composite of about 60 wt % h-BN as potentially a high thermal conductivity electrical insulator. The composite is a related material, not the grades listed in properties.
source: nasa-2017-hbn
where: Summary and Introduction
- application: electronics-and-chips
device: Microwave components and high-temperature electrical insulators
example: Precision Ceramics lists microwave components, high-temperature electrical insulators, radar components, setter plates, crucibles and metal spraying nozzles as applications of its hot-pressed Grade A.
source: pc-uk-grade-a
where: Overview and Applications block
- application: mechanisms
device: Solid lubricant
example: Wikipedia says h-BN is a good lubricant at low and high temperatures, usable up to 900 °C including in oxidizing atmospheres, and that its lubricity does not depend on trapped water or gas, so it can be used in vacuum, including space applications.
source: wiki-bn
where: Applications, Hexagonal BN paragraph
supply:
- subject: Boron feedstock for h-BN (borates)
abundance: 'USGS 2026: Turkey produced 1,500 thousand metric tons of refined borates in 2025 (1,800 in 2024) and holds reserves of 950,000 thousand metric tons, the largest in the table. The United States reports reserves of 48,000 thousand metric tons. Turkey supplied 90 % of U.S. boron imports in 2021 to 2024.'
critical_lists:
- list: U.S. Final 2025 List of Critical Minerals (boron added in 2025)
listed: true
source: usgs-mcs2026-boron
where: Salient Statistics, Import Sources, World Production and Reserves table, Critical minerals paragraph
- subject: Producers named for hot-pressed h-BN grades in the sources read
abundance: NASA 2020 lists Saint-Gobain (HP, M26, M), Kennametal (BN-XX) and Tokuyama or Precision Ceramics (Hi-M). Precision Ceramics UK sells Grade A. NASA 2017 used Momentive PT110 powder as the h-BN starting material. Stanford Advanced Materials is a distributor of hot-pressed BN.
source: nasa-2020-bn
where: Materials of Interest table, Vendor column; the Momentive note is in nasa-2017-hbn, Experimental section
documents:
- title: 'Wikipedia: Boron nitride (structure, physical properties, applications)'
type: database
url: https://en.wikipedia.org/wiki/Boron_nitride
- title: 'PubChem compound record CID 66227: Boron nitride, GHS classification and identifiers'
type: database
url: https://pubchem.ncbi.nlm.nih.gov/compound/Boron-nitride
- title: Lot-to-lot Variability of BN Grades for Space Electric Propulsion Applications (Mackey et al., NASA Glenn and JPL, 2020, NTRS 20200000860)
type: report
url: https://ntrs.nasa.gov/citations/20200000860
year: 2020
- title: Synthesis and Thermal Conductivity of Exfoliated Hexagonal Boron Nitride/Alumina Ceramic Composite (NASA/TM-2017-219472)
type: report
url: https://ntrs.nasa.gov/api/citations/20170003135/downloads/20170003135.pdf
year: 2017
- title: 'USGS Mineral Commodity Summaries 2026: Boron'
type: report
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-boron.pdf
year: 2026
- title: 'Khan et al., Hexagonal Boron Nitride Single Crystal Thermal Oxidation and Etching in Air: An AFM Study, MRS Advances 4(10), 2019'
type: paper
url: https://www.cambridge.org/core/journals/mrs-advances/article/abs/hexagonal-boron-nitride-single-crystal-thermal-oxidation-and-etching-in-air-an-atomic-force-microscopy-study/A25F5711618A9A69FBDD989C3BDBBFC8
year: 2019
- title: 'Precision Ceramics UK material datasheet: Boron Nitride (BN) Grade A'
type: datasheet
url: https://precision-ceramics.com/wp-content/uploads/2018/07/Boron-Nitride-Grade-A-Technical-Data-Sheet-en.pdf
- title: 'Stanford Advanced Materials: Hot Pressed Boron Nitride Crucible specification table (BN99 AX05, BN-BO Grade A, BNCB Grade HP)'
type: datasheet
url: https://samaterials.com/boron-nitride/1659-boron-nitride-crucible.html
gaps:
- Momentive PT110 powder datasheet and the Saint-Gobain boron nitride technical pages returned HTTP 403 and were not read. No Saint-Gobain or Momentive value is recorded for any grade.
- The NASA 2020 density table is ambiguous in the extracted PDF text (geometric, Archimedes and porosimetry columns are not separable), so no HP density is recorded. Grade A density is used instead.
- The NASA Lot 1 thermal block also gives HP conductivity at 700 °C (26 W/m-K) and specific heat at 100 °C (1000 and 988 J/kg-K), and an emissivity table, but the extracted text mixes Lot 1 and Lot 2 blocks, so these are left out.
- 'Thermal conductivity of Grade A and HP at elevated temperature was not recorded: the datasheet gives no temperature for its conductivity row.'
- 'Flexural strength of the HP grade on the NASA slide: sample condition (as-machined, dry oven or humidity chamber) and lot are not separated in the table. The moisture-soak strength values were not recorded.'
- Production route of h-BN powder and hot-pressed blanks was not found in a readable source. The Wikipedia page was read for structure, applications and reference titles only; its synthesis text was not reachable in the fetched excerpt.
- Fracture toughness, compressive strength of the HP and M grades, and any h-BN-specific hardness value were not found in the sources read.
- Erosion rate, secondary electron emission yield and outgassing (total mass loss) for hot-pressed h-BN in space were not found; the NASA 2020 report lists these as factors of interest but the numbers were not in the text read.
- Weibull modulus, porosity, emissivity and first-oxidation temperature are not in the canonical property file. The first two names are used as printed; the first-oxidation name is first_oxidation_temperature. Check against property-canon.yaml before import.
- Density and thermal conductivity from Wikipedia are material-level values for h-BN and not for any hot-pressed grade; they are labelled as such.
- The SAM density and compressive strength values for hot-pressed grades are labelled by SAM as theoretical values and were not recorded.
- The NASA 2017 hBN/alumina composite values (86 and 18 W/mK at room temperature, density 2.45 g/cm3) are for a composite of about 60 wt % h-BN and 40 wt % alumina and are not recorded as h-BN properties.
- 'Tags: no tags.environments entry, because no fetched source ties hot-pressed h-BN to a named orbital or planetary environment.'
- 'Designations: no AISI, UNS, EN, DIN, JIS or AFNOR code exists for hexagonal BN in the sources read. Trade-name designations only, and PT110 is a powder feedstock, not a dense ceramic.'
- Atomic weights of boron and nitrogen were not read in this run, so the recipe lists atom counts only. PubChem prints a molecular weight of 24.82 g/mol for BN.
- Grade A dissipation factor at 1 MHz (printed as 1.2E-3 parallel and 3.4E-3 perpendicular) was removed because the printed scientific notation did not match the value check; the datasheet value is not recorded.
sources:
wiki-bn:
title: Boron nitride, Wikipedia
url: https://en.wikipedia.org/wiki/Boron_nitride
kind: web
license: CC BY-SA, cited not reproduced
pubchem-bn:
title: 'PubChem compound record: Boron Nitride, CID 66227 (ECHA C&L Inventory classification, identifiers and uses)'
id: CAS 10043-11-5, EC 233-136-6
url: https://pubchem.ncbi.nlm.nih.gov/compound/Boron-nitride
kind: database
license: PubChem (NCBI), public domain; sections attributed to ECHA, CIR and others
nasa-2020-bn:
title: Lot-to-lot Variability of BN Grades for Space Electric Propulsion Applications (Mackey, Salem, Stanford, Kamhawi, McEnerney, Hofer)
id: NTRS 20200000860, 2020
url: https://ntrs.nasa.gov/citations/20200000860
year: 2020
kind: report
license: public domain (NASA)
nasa-2017-hbn:
title: Synthesis and Thermal Conductivity of Exfoliated Hexagonal Boron Nitride/Alumina Ceramic Composite (Hung, Hurst, Santiago, Lizcano, Kelly)
id: NASA/TM-2017-219472, NTRS 20170003135
url: https://ntrs.nasa.gov/api/citations/20170003135/downloads/20170003135.pdf
year: 2017
kind: report
license: public domain (NASA)
usgs-mcs2026-boron:
title: Mineral Commodity Summaries 2026, Boron
id: USGS MCS 2026
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-boron.pdf
year: 2026
kind: report
license: public domain (USGS)
khan2019-hbn-oxidation:
title: 'Hexagonal Boron Nitride Single Crystal Thermal Oxidation and Etching in Air: An Atomic Force Microscopy Study (Khan, Nour, Mondoux, Liu, Edgar, Berta)'
id: DOI 10.1557/adv.2018.667, MRS Advances 4(10), 601-608
url: https://www.cambridge.org/core/journals/mrs-advances/article/abs/hexagonal-boron-nitride-single-crystal-thermal-oxidation-and-etching-in-air-an-atomic-force-microscopy-study/A25F5711618A9A69FBDD989C3BDBBFC8
year: 2019
kind: paper
license: Materials Research Society, abstract read, cited not reproduced
pc-uk-grade-a:
title: 'Precision Ceramics UK, Material Datasheet: Boron Nitride (BN) Grade A'
url: https://precision-ceramics.com/wp-content/uploads/2018/07/Boron-Nitride-Grade-A-Technical-Data-Sheet-en.pdf
year: 2018
kind: datasheet
license: Manufacturer datasheet, cited not reproduced
sam-bn-hp:
title: Stanford Advanced Materials, Hot Pressed Boron Nitride Crucible, specification table (BN99 AX05, BN-BO Grade A, BNCB Grade HP)
url: https://samaterials.com/boron-nitride/1659-boron-nitride-crucible.html
kind: web
license: Supplier web page, cited not reproduced
license: CC-BY-4.0
updated: '2026-10-26'
review:
status: draft
method: assistant
checked_values: 34
unreachable: 2
caveats: 5
note: 'Values were read by an AI assistant on 2026-10-26 from the datasheet PDF, NASA report PDF and the web pages named in each entry. Unreachable: Momentive PT110 datasheet and Saint-Gobain boron nitride pages (HTTP 403). Caveats: Grade A datasheet values are mean and typical values, not guarantees; NASA HP values are from one lot with lot ambiguity on some slides; Wikipedia values are material-level and not grade-level; the first-oxidation value is from a single crystal, not a hot-pressed grade; the 1,500 thousand t Turkey figure is USGS production of refined borates, not h-BN production.'
story:
recipe:
line: 'h-BN is the hexagonal form of boron nitride, with boron and nitrogen bonded in layers and van der Waals forces between layers. Its density is 2.1 g/cm3 (Wikipedia). BN has a molar mass of 24.82 g/mol (PubChem). Hot-pressed ceramic grades are made by hot pressing h-BN powder with a binder: NASA''s HP grade contains a calcium borate binder and a BN phase of 98 wt % by Rietveld refinement, and Stanford Advanced Materials lists the Grade A binder as B2O3 (SAM).'
parts:
- name: Boron
symbol: B
role: One boron atom per formula unit, bonded to nitrogen within each layer
- name: Nitrogen
symbol: 'N'
role: One nitrogen atom per formula unit, bonded to boron within each layer
risk_groups:
- title: For people
lead: The classification depends on who notified it, and the sources do not give exposure limits.
level: 1
verdict: Mixed notifications
points:
- label: Boron nitride as a substance
line: Of 480 company reports to the European chemicals agency, 422 say it does not meet GHS criteria. Among those that gave codes, H319 (serious eye irritation, 11.7 %) and H335 (respiratory irritation, 10.8 %) are the most common.
- label: Cosmetic use
line: The cosmetic review summarised by PubChem finds it safe in present practices of use and concentration.
- title: If it fails
lead: These failures are from the sources read. The bending data are measured at NASA, the oxidation data are from a single crystal study.
points:
- label: Hot strength
line: HP bending strength parallel to pressing falls from 39.7 MPa at 25 °C to 9.8 MPa at 600 °C.
- label: Air
line: In ambient air, single h-BN crystals first show oxidation pits at 900 °C after 20 minutes.
- label: Lot change
line: NASA finds that flexural strength and elastic modulus vary significantly between lots, so a grade name alone does not fix the strength.
- title: Handling and storage
points:
- label: Specify direction and lot
line: Strength differs parallel and perpendicular to pressing, and between lots. Name the grade, the pressing direction and the lot.
- label: Temperature
line: Grade A is rated to 850 °C in air and 1200 °C in inert atmosphere.
why: h-BN is an electrical insulator that also conducts heat well for an insulator. In Precision Ceramics Grade A, a hot-pressed grade, the dielectric strength is 88 kV/mm and the thermal conductivity is 30 W/(m·K) parallel and 34 W/(m·K) perpendicular to pressing. Its air limit is 850 °C. These properties suit microwave parts and high-temperature insulators. NASA tested hot-pressed h-BN grades for space electric propulsion, where parts must insulate electrically and thermally.
uses:
- where: Electric propulsion
line: NASA Glenn and JPL tested several commercial hot-pressed h-BN grades for space electric propulsion, where parts must insulate electrically and thermally.
- where: Microwave and high-temperature insulators
line: Precision Ceramics lists microwave components, radar components and high-temperature electrical insulators among the uses of Grade A.
- where: Solid lubricant
line: Wikipedia says h-BN is a good lubricant up to 900 °C, including in oxidizing atmospheres and in vacuum.
can_do:
- label: Insulate electrically
value: 88 kV/mm
benchmark: dielectric_strength
line: Grade A has a DC dielectric strength of 88 kV/mm, and a dielectric constant of 4.6 parallel and 4.2 perpendicular at 1 MHz.
- label: Carry heat
value: 30 to 34 W/(m·K)
benchmark: thermal_conductivity
line: Grade A conducts heat at 30 W/(m·K) parallel and 34 W/(m·K) perpendicular to pressing. The NASA HP grade gives 33 and 31 W/(m·K).
- label: Work hot
value: 850 °C in air
benchmark: max_service_temp
line: Grade A is rated to 850 °C in air and 1200 °C in an inert atmosphere, per the datasheet. These are manufacturer figures, not component allowables.
compare: 'In this profile the in-plane thermal conductivity of hot-pressed grades, 30 to 34 W/(m·K) for Grade A and 33 for HP, is about one-twentieth of the 600 W/(m·K) that Wikipedia gives for h-BN along the basal planes. Pressing and binder content set how much of that ideal conductivity a grade keeps. The strength also changes most with direction: Grade A reaches 94 MPa parallel and 65 MPa perpendicular, while the HP grade reverses that order at 39.7 and 70.5 MPa.'
compare_rows:
- label: Density
benchmark: density
- label: Thermal conductivity
benchmark: thermal_conductivity
- label: Flexural strength
benchmark: flexural_strength
handling:
- Name the grade, the hot-press direction and the lot, because strength and conductivity change with each.
- Keep Grade A below 850 °C in air. Above about 900 °C in air, single crystals oxidise.
- Limit dust. PubChem lists precautionary codes for dust and eye protection.
good_for:
- 'Electrical insulation at high temperature: 88 kV/mm dielectric strength in Grade A.'
- 'Heat conduction in an insulator: 30 to 34 W/(m·K) in Grade A, and 600 W/(m·K) along the basal planes of h-BN.'
- Lubrication up to 900 °C, including in vacuum.
watch_out:
- 'Hot strength: HP bending strength parallel to pressing is 9.8 MPa at 600 °C, against 39.7 MPa at 25 °C.'
- 'Direction and lot: strength changes with pressing direction and between lots, and the trend reverses between grades.'
- 'Oxidation: single crystals show pits in air from 900 °C after 20 minutes.'
- 'Moisture: NASA reports moisture sensitivity of flexural strength and modulus, most in one lot.'
- No erosion yield, outgassing or radiation value for hot-pressed h-BN was found in the sources read, so space-environment durability is not established here.
verdict: Hot-pressed h-BN is an insulator that resists thermal shock, with 88 kV/mm dielectric strength and an 850 °C air limit for Grade A. Its strength depends strongly on pressing direction, lot and temperature, and it oxidises in air from about 900 °C. NASA has tested grades for electric propulsion, but no space-environment erosion or outgassing number is in this profile.
References
Every number above carries a reference number. Click one to see the source and where in it the value comes from.