spore: profile
id: pg
spore_version: 0.2
family: carbon-materials
name: Pyrolytic graphite
abbreviation: PG
role: thermally anisotropic carbon, deposited from hydrocarbon gas and used for heat spreading and atomic-oxygen tests in orbit
category: carbon
type: Graphite
summary: |
  Pyrolytic graphite is a dense, layered carbon made by heating a hydrocarbon gas until it decomposes and the carbon deposits as graphite. Its heat conduction is strongly directional: a datasheet quotes thermal conductivity of 80 to 240 W/m K at 0 to 100 °C, while a secondary source quotes up to 1700 W/mK in the basal plane and 10 W/mK across it. In low Earth orbit on NASA's MISSE 2 tray, its atomic oxygen erosion yield was 4.15e-25 cm3/atom, a value that the predictive tool estimated at 3.73e-25 cm3/atom.
best_for: Heat spreading in one direction, where a thin, light carbon layer must carry heat away along its plane
weakest_at: 'Strong anisotropy: heat conducts poorly across the layers, and the material is costly to make at high temperature'
identity:
  formula: C
  cas: 7440-44-0
  crystal_system: hexagonal
  space_group: P63mc (buckled) or P63/mmc (flat)
  source: wiki-graphite
  where: Infobox (formula C, hexagonal or rhombohedral, space group P63mc or P63/mmc); CAS 7440-44-0 from the OSHA chemical data page for graphite (synthetic)
tags:
  environments:
    - low-earth-orbit
  stresses:
    - atomic-oxygen
  applications:
    - thermal-control
properties:
  - benchmark: atomic_oxygen_erosion_yield
    value: 4.15e-25
    unit: cm3/atom
    scope: material
    conditions:
      exposure: MISSE 2 PEACE tray outside the ISS Quest airlock, 2001 to 2005
      atomic_oxygen_fluence: 8.43e21 atoms/cm2
      environment: low Earth orbit
    method: Measured mass loss from the flown sample, reported as erosion yield by NASA
    status: flight
    source: nasa-ao-2008
    where: Table I, MISSE 2 PEACE polymers erosion yield data (pyrolytic graphite row); repeated in the measured table, MISSE 2 column
  - benchmark: atomic_oxygen_erosion_yield
    value: 3.73e-25
    unit: cm3/atom
    scope: material
    conditions:
      exposure: predicted for the same MISSE 2 exposure
      atomic_oxygen_fluence: 8.43e21 atoms/cm2
    method: Value from the NASA predictive tool, shown next to the flown result for comparison
    status: calculated
    source: nasa-ao-2008
    where: Measured atomic oxygen erosion yields table, Predicted column (pyrolytic graphite row)
  - benchmark: density
    value: 2.25
    unit: g cm-3
    scope: material
    conditions:
      temperature: 20 °C
      grade: pyrolytic graphite disc, 99.99% purity, as rolled
    method: Datasheet value for a commercial pyrolytic graphite disc
    status: ground
    source: goodfellow-pg
    where: Physical properties, Density (product page for pyrolitic graphite disc)
  - benchmark: thermal_conductivity
    value: 80
    value_high: 240
    unit: W m-1 K-1
    scope: material
    conditions:
      temperature: 0 to 100 °C
      grade: commercial pyrolytic graphite disc (direction not stated on the page)
    method: Datasheet range printed as 80-240 W m-1 K-1 at 0-100 °C
    status: ground
    source: goodfellow-pg
    where: Thermal properties, Thermal conductivity (pyrolitic graphite disc)
  - benchmark: thermal_conductivity
    value: 1700
    unit: W/mK
    scope: material
    conditions:
      direction: basal plane (in-plane)
      form: pyrolytic graphite, formed from the gas phase
    method: Upper value quoted for in-plane conductivity in a secondary article; not a measured result in this profile
    status: ground
    source: electronics-cooling
    where: Article text on pyrolytic graphite, basal-plane thermal conductivity
  - benchmark: thermal_conductivity
    value: 10
    unit: W/mK
    scope: material
    conditions:
      direction: perpendicular to the basal plane (through-plane)
      form: pyrolytic graphite
    method: Value quoted in the same secondary article as the basal-plane figure
    status: ground
    source: electronics-cooling
    where: Article text on pyrolytic graphite, perpendicular conductivity
  - benchmark: specific_heat
    value: 712
    unit: J K-1 kg-1
    scope: material
    conditions:
      temperature: 25 °C
      grade: pyrolytic graphite disc
    method: Datasheet value
    status: ground
    source: goodfellow-pg
    where: Thermal properties, Specific heat (pyrolitic graphite disc)
  - benchmark: cte
    value: 0.6
    value_high: 4.3
    unit: x10-6 K-1
    scope: material
    conditions:
      temperature: 0 to 100 °C
      grade: pyrolytic graphite disc
    method: Datasheet range, printed as 0.6-4.3 x10-6 K-1 at 0-100 °C
    status: ground
    source: goodfellow-pg
    where: Thermal properties, Coefficient of thermal expansion
  - benchmark: melting_point
    value: 3650
    unit: °C
    scope: material
    conditions:
      grade: pyrolytic graphite disc
    method: Datasheet value
    status: ground
    source: goodfellow-pg
    where: Thermal properties, Melting point
  - benchmark: electrical_resistivity
    value: 1375
    unit: µOhm cm
    scope: material
    conditions:
      temperature: 0 °C
      grade: pyrolytic graphite disc
    method: Datasheet value
    status: ground
    source: goodfellow-pg
    where: Electrical properties, Electrical resistivity
  - benchmark: elastic_modulus
    value: 4.8
    unit: GPa
    scope: material
    conditions:
      basis: tensile modulus; the datasheet states no test condition
      grade: pyrolytic graphite disc
    method: Datasheet value, as printed
    status: ground
    source: goodfellow-pg
    where: Mechanical properties, Tensile modulus
  - benchmark: osha_pel_respirable
    value: 5
    unit: mg/m3
    scope: material
    conditions:
      basis: OSHA permissible exposure limit, time-weighted average, respirable fraction, for graphite (synthetic) CAS 7440-44-0
    method: Regulatory limit as printed on the OSHA chemical data page
    status: ground
    source: osha-synthetic
    where: Exposure limits, OSHA PEL-TWA (15 mg/m3 total dust, 5 mg/m3 respirable fraction)
risks:
  hazards:
    - text: Dust is the hazard listed for graphite. OSHA sets a PEL-TWA of 15 mg/m3 total dust and 5 mg/m3 respirable fraction for graphite (synthetic); the NIOSH REL is not given there.
      ghs: []
      source: osha-synthetic
      where: Exposure limits
    - text: For natural graphite, OSHA lists a PEL of 15 mppcf, NIOSH a REL of 2.5 mg/m3 (respirable) and an IDLH of 1250 mg/m3. Pyrolytic graphite is not the natural mineral, so these limits are a guide for handling dust.
      ghs: []
      source: osha-natural
      where: Exposure limits (CAS 7782-42-5)
  failure_risks:
    - mode: Atomic oxygen erosion in low Earth orbit
      trigger: Exposure to atomic oxygen, at a fluence of 8.43e21 atoms/cm2 over about 4 years on MISSE 2
      consequence: Surface recession of 4.15e-25 cm3/atom erosion yield (the flown value), which the predictive tool estimated at 3.73e-25 cm3/atom.
      severity: low
      source: nasa-ao-2008
      where: Table I and measured table, MISSE 2 PEACE
  side_effects:
    - text: The thermal conductivity is anisotropic, about 1700 W/mK in the basal plane against 10 W/mK across it, so a pyrolytic graphite part works as a heat spreader in its plane, not as a through-thickness conductor.
      affects: Designers who assume isotropic conduction
      source: electronics-cooling
      where: Article text on basal-plane and perpendicular conductivity
  handling:
    - text: 'Dust control: the OSHA limits for graphite are 15 mg/m3 total dust and 5 mg/m3 respirable fraction (synthetic), so use local exhaust where machining or grinding makes dust.'
      source: osha-synthetic
      where: Exposure limits
  mitigations:
    - text: Use the in-plane direction for heat spreading and do not rely on through-plane conduction; the NASA erosion test shows that the flown sample survived atomic oxygen with a yield of 4.15e-25 cm3/atom.
      source: nasa-ao-2008
      where: Table I
corrosion:
  - environment: Atomic oxygen in low Earth orbit (MISSE 2 PEACE tray, ISS)
    headline: In low Earth orbit the erosion yield was 4.15e-25 cm3/atom after an atomic oxygen fluence of 8.43e21 atoms/cm2.
    effect: NASA flew pyrolytic graphite on the MISSE 2 PEACE tray and measured its erosion yield. The predictive tool, which fits the MISSE 2 data, estimated 3.73e-25 cm3/atom, so the flown and predicted values agree to within about 11%. The report also lists atomic oxygen fluence as the controlling exposure.
    rating: low
    conditions:
      exposure: outside the Quest airlock of the ISS, 2001 to 2005
      fluence: 8.43e21 atoms/cm2
      duration: about 3.95 years (MISSE 2 PEACE exposure)
    source: nasa-ao-2008
    where: Table I; Measured atomic oxygen erosion yields table; section 2.1 exposure details
  - environment: Thermal cycling in the MISSE 2 tray
    headline: The flight tray was not reported to have failed under thermal cycling, but the report gives no separate result for pyrolytic graphite.
    effect: No separate thermal-cycling result for pyrolytic graphite was found in the source. The nominal base-plate range was -30 to 40 °C; this is a condition of the exposure, not a measured effect on PG.
    rating: low
    conditions:
      range: nominal base-plate range, -30 to 40 °C
      material: pyrolytic graphite on the MISSE 2 PEACE tray
    source: nasa-ao-2008
    where: Section 2.1 exposure details
supply:
  - subject: Natural graphite (mine feedstock; pyrolytic graphite itself is made from a hydrocarbon gas)
    abundance: Not quantified for pyrolytic graphite. The USGS world resources of graphite are described as exceeding 800 million tons of recoverable graphite outside the United States.
    producers:
      - country: China
        share_percent: 77.8
        year: 2025
      - country: Madagascar
        share_percent: 4.4
        year: 2025
      - country: Brazil
        share_percent: 3.6
        year: 2025
      - country: Mozambique
        share_percent: 3.3
        year: 2025
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (final, published 6 November 2025)
        listed: true
      - list: EU critical raw materials list
        listed: false
    recycling: 'USGS: information on the quantity and value of recycled graphite was not available, and the abundance of graphite in the world market inhibits recycling efforts.'
    substitutes:
      - 'USGS: synthetic graphite powder and secondary synthetic graphite from machined shapes compete for battery applications.'
    source: usgs-mcs2026-graphite
    where: 'World Mine Production and Reserves table, 2025e (1,800,000 t world total, rounded; shares calculated by Space Mushroom from the printed production figures: China 1,400,000 t, Madagascar 80,000 t, Brazil 65,000 t, Mozambique 60,000 t); Recycling; Substitutes; critical list from usgs-critical-2025'
media: []
documents:
  - title: 'NASA/TM-2008-215490: Atomic Oxygen Erosion Yield Predictive Tool for Spacecraft Polymers in Low Earth Orbit'
    type: report
    url: https://ntrs.nasa.gov/citations/20090011780
    year: 2008
  - title: 'USGS Mineral Commodity Summaries 2026: Graphite (natural)'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-graphite.pdf
    year: 2026
  - title: 'Goodfellow: Pyrolytic Graphite Carbon Disk (product and datasheet page)'
    type: datasheet
    url: https://www.goodfellow.com/usa/pyrolytic-graphite-disc-group
    year: 2026
  - title: Low temperature transport properties of pyrolytic graphite sheet (arXiv:1704.03204)
    type: paper
    url: https://arxiv.org/pdf/1704.03204
    year: 2017
  - title: 'OSHA chemical data: Graphite (synthetic), CAS 7440-44-0'
    type: standard
    url: https://www.osha.gov/chemicaldata/533
    year: 2021
  - title: 'OSHA chemical data: Graphite (natural), respirable fraction, CAS 7782-42-5'
    type: standard
    url: https://www.osha.gov/chemicaldata/665
    year: 2021
gaps:
  - No flight result for pyrolytic graphite beyond MISSE 2 erosion yield; no thermal-vacuum, radiation or UV exposure result found for pyrolytic graphite.
  - The atomic oxygen erosion yield is not a canonical property name, so it is written as atomic_oxygen_erosion_yield.
  - PubChem GHS classification could not be read in this run (the page returned a browser check), so no GHS entry is given.
  - NIOSH Pocket Guide entry for graphite (natural) was not reached; the limits come from the OSHA chemical data pages.
  - The 1700 W/mK and 10 W/mK values come from a secondary article, not from a manufacturer datasheet; the MINTEQ Pyroid datasheet returned HTTP 403.
  - The pyrolytic graphite sheet arXiv paper gives thickness and temperature ranges but no thermal conductivity or density values for pyrolytic graphite, so it is cited for the thermal-link use only.
  - Pyrolytic-graphite-specific supply is not quantified; the supply shares are for natural graphite, the mine feedstock, not for pyrolytic deposition.
  - The Wikipedia Pyrolytic carbon article gives no density or thermal conductivity number and no deposition temperature for manufacture.
sources:
  nasa-ao-2008:
    title: Atomic Oxygen Erosion Yield Predictive Tool for Spacecraft Polymers in Low Earth Orbit
    id: NASA/TM-2008-215490 (Banks, Backus and de Groh, December 2008)
    url: https://ntrs.nasa.gov/citations/20090011780
    year: 2008
    kind: report
    license: NASA public domain (cited)
  usgs-mcs2026-graphite:
    title: 'USGS Mineral Commodity Summaries 2026: Graphite (natural)'
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-graphite.pdf
    year: 2026
    kind: report
    license: US government work (cited)
  usgs-critical-2025:
    title: Interior Department releases final 2025 List of Critical Minerals
    id: USGS science snippet, 14 November 2025
    url: https://www.usgs.gov/news/science-snippet/interior-department-releases-final-2025-list-critical-minerals
    year: 2025
    kind: web
    license: US government work (cited)
  goodfellow-pg:
    title: 'Goodfellow: Pyrolytic Graphite Carbon Disk, 99.99% purity, product datasheet'
    id: Goodfellow Metals, grade Pyrolitic Graphite, SKU 1000037214-group
    url: https://www.goodfellow.com/usa/pyrolytic-graphite-disc-group
    year: 2026
    kind: datasheet
    license: Goodfellow terms (cited)
  electronics-cooling:
    title: 'Electronics Cooling: thermal management article on pyrolytic graphite sheet'
    id: electronics-cooling.com, article p=218
    url: https://www.electronics-cooling.com/?p=218
    year: 2026
    kind: web
    license: cited
  arxiv-pgs-2017:
    title: Low temperature transport properties of pyrolytic graphite sheet
    id: arXiv:1704.03204 (Nakamura, Miyafuji, Fujii, Matsui, Fukuyama)
    url: https://arxiv.org/pdf/1704.03204
    year: 2017
    kind: paper
    license: arXiv (cited)
  wiki-pyrolytic-carbon:
    title: 'Wikipedia: Pyrolytic carbon'
    id: en.wikipedia.org, Pyrolytic_carbon
    url: https://en.wikipedia.org/wiki/Pyrolytic_carbon
    year: 2026
    kind: web
    license: CC BY-SA 4.0 (cited)
  wiki-graphite:
    title: 'Wikipedia: Graphite'
    id: en.wikipedia.org, Graphite
    url: https://en.wikipedia.org/wiki/Graphite
    year: 2026
    kind: web
    license: CC BY-SA 4.0 (cited)
  wiki-carbon:
    title: 'Wikipedia: Carbon'
    id: en.wikipedia.org, Carbon (standard atomic weight from CIAAW 2021)
    url: https://en.wikipedia.org/wiki/Carbon
    year: 2026
    kind: web
    license: CC BY-SA 4.0 (cited)
  osha-synthetic:
    title: 'OSHA chemical data: Graphite (synthetic)'
    id: CAS 7440-44-0, OSHA chemical sampling data
    url: https://www.osha.gov/chemicaldata/533
    year: 2021
    kind: standard
    license: US government work (cited)
  osha-natural:
    title: 'OSHA chemical data: Graphite (natural), respirable fraction'
    id: CAS 7782-42-5, OSHA chemical sampling data
    url: https://www.osha.gov/chemicaldata/665
    year: 2021
    kind: standard
    license: US government work (cited)
review:
  status: draft
  method: assistant
  checked_values: 12
  note: Values read by an AI assistant from pages fetched in this run; the MISSE 2 flight record and the Goodfellow datasheet are the primary values.
story:
  recipe:
    line: Pyrolytic graphite is pure carbon. It is made by heating a hydrocarbon gas nearly to its decomposition temperature so that the carbon deposits as graphite, the layered hexagonal form of carbon.
    parts:
      - name: Carbon
        symbol: C
        atoms: 1
        atomic_weight: 12.011
        role: The only element in the material. Carbon atoms form flat hexagonal sheets, and the sheets stack into the layered structure that makes conduction strongly directional.
  risk_groups:
    - title: For people
      level: 0
      verdict: Dust is the main concern
      lead: Pyrolytic graphite is a carbon material with OSHA exposure limits for graphite dust. No hazard classification was read in this run.
      points:
        - label: Dust
          line: OSHA sets a limit of 15 mg/m3 for total dust and 5 mg/m3 for respirable dust for synthetic graphite, so machining and grinding need dust control.
        - label: Natural graphite
          line: For natural graphite, NIOSH sets a respirable REL of 2.5 mg/m3 and an IDLH of 1250 mg/m3.
    - title: In orbit
      lead: The orbital data concern the surface, not the health of people.
      points:
        - label: Atomic oxygen
          line: On the MISSE 2 tray the erosion yield was 4.15e-25 cm3/atom, with an atomic oxygen fluence of 8.43e21 atoms/cm2.
  why: Pyrolytic graphite is a layered carbon whose heat conduction is far higher along its planes than across them. It combines a density of 2.25 g/cm3 with a specific heat of 712 J K-1 kg-1 at room temperature, so it stores and spreads heat efficiently in one direction. Its atomic oxygen erosion in low Earth orbit was measured on NASA's MISSE 2 tray.
  uses:
    - where: Heat spreading in electronics
      line: A secondary article describes pyrolytic graphite as having a basal-plane conductivity up to 1700 W/mK. The same article says it has found use in high-performance, niche aerospace applications.
    - where: Thermal link in cryogenic systems
      line: A 2017 study of pyrolytic graphite sheet measured its low-temperature transport properties and describes it as a light, highly conducting thermal link over a wide temperature range.
    - where: Atomic-oxygen exposure in low Earth orbit
      line: NASA flew pyrolytic graphite on the MISSE 2 tray outside the ISS airlock, with an erosion yield of 4.15e-25 cm3/atom.
  can_do:
    - label: Thermal conduction
      benchmark: thermal_conductivity
      value: '80'
      line: A datasheet quotes thermal conductivity of 80 to 240 W m-1 K-1 at 0 to 100 °C for a commercial pyrolytic graphite disc. A secondary source quotes up to 1700 W/mK in the basal plane and 10 W/mK across it.
    - label: Density
      benchmark: density
      value: '2.25'
      line: The datasheet density is 2.25 g/cm3 at 20 °C.
    - label: Orbital survival
      benchmark: atomic_oxygen_erosion_yield
      value: '4.15e-25'
      line: On MISSE 2 it recorded 4.15e-25 cm3/atom after about 4 years in low Earth orbit, and the NASA predictive tool estimated 3.73e-25 cm3/atom.
  compare: Pyrolytic graphite is a dense, thermally anisotropic carbon. Its in-plane conductivity is far higher than most materials in this collection, but across the layers it is much lower, so it suits in-plane heat spreading. The table compares it with other materials on conductivity, density and the orbital erosion measurement.
  compare_rows:
    - label: Thermal conductivity
      benchmark: thermal_conductivity
    - label: Density
      benchmark: density
    - label: Atomic oxygen erosion yield
      benchmark: atomic_oxygen_erosion_yield
  handling:
    - 'Dust is the hazard for graphite: keep dust below the OSHA limits with local exhaust in machining and grinding.'
    - Use the material in its plane for heat spreading; it conducts far less across the layers.
    - In low Earth orbit the surface recedes by atomic oxygen erosion, at 4.15e-25 cm3/atom on MISSE 2.
  good_for:
    - In-plane heat spreading, where a light, thin carbon layer carries heat along its plane.
    - Carbon flown on NASA's MISSE 2 tray, with a documented erosion yield for low Earth orbit.
  watch_out:
    - 'Strong anisotropy: 1700 W/mK in the basal plane against 10 W/mK across it, so it is a poor through-thickness conductor.'
    - Costly to make, because the deposition needs very high temperatures; a secondary article says so without giving a process value.
  verdict: Pyrolytic graphite is a directional heat spreader with a measured orbital erosion yield. It is the right choice when heat must travel in one plane, and the wrong choice when it must cross the layers.