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.