spore: profile
id: silica-aerogel
spore_version: 0.2
family: aerogels
name: Silica aerogel
abbreviation: SiO2 aerogel
role: thermal insulator and dust collector
category: thermal-protection
type: aerogels
summary: |
  Silica aerogel is a porous silica solid that is about 99 % air by volume, as a JPL article describes it. Pyrogel XTE, a commercial silica aerogel blanket from Aspen Aerogels, has a nominal density of 200 kg/m3 and a conductivity of 14 mW/(m·K) at 0 °C. NASA's Stardust mission used a flight-spare silica aerogel, at about 0.01 g/cm3, to catch comet and interstellar dust.
best_for: Very low thermal conductivity per thickness at cold and moderate temperatures
weakest_at: Upper temperature limit of the Pyrogel XTE grade (650 °C) and its rising conductivity with temperature
identity:
  formula: Porous amorphous silica (SiO2) network with air in the pores; the JPL article describes it as 99 % air
  source: nasa-jpl-colonize-mars
  where: Opening description of the article
tags:
  environments:
    - mars-surface
  stresses:
    - thermal-cycling
    - extreme-cold
  applications:
    - thermal-control
properties:
  - benchmark: density
    label: Nominal apparent density, Pyrogel XTE
    value: 200
    unit: kg/m3
    scope: material
    conditions:
      product: Pyrogel XTE blanket
      tolerance: plus or minus 10 %
    method: Nominal value printed on the Pyrogel XTE technical data page
    status: ground
    source: aerogel-uk-pyrogel-xte
    where: Technical data section, Nominal Apparent Density
  - benchmark: thermal_conductivity
    label: Thermal conductivity, Pyrogel XTE at 0 °C
    value: 14
    unit: mW/(m·K)
    scope: material
    conditions:
      temperature: 0 °C
      product: Pyrogel XTE blanket
    method: Value printed on the Pyrogel XTE technical data page; test standard and load not stated on that page
    status: ground
    source: aerogel-uk-pyrogel-xte
    where: Technical data section, Thermal Conductivity
  - benchmark: thermal_conductivity
    label: Thermal conductivity, Pyrogel XTE at 300 °C
    value: 24
    unit: mW/(m·K)
    scope: material
    conditions:
      temperature: 300 °C
      product: Pyrogel XTE blanket
    method: Value printed on the Pyrogel XTE technical data page; test standard and load not stated on that page
    status: ground
    source: aerogel-uk-pyrogel-xte
    where: Technical data section, Thermal Conductivity
  - benchmark: thermal_conductivity
    label: Thermal conductivity, Pyrogel XTE at 600 °C
    value: 62
    unit: mW/(m·K)
    scope: material
    conditions:
      temperature: 600 °C
      product: Pyrogel XTE blanket
    method: Value printed on the Pyrogel XTE technical data page; test standard and load not stated on that page
    status: ground
    source: aerogel-uk-pyrogel-xte
    where: Technical data section, Thermal Conductivity
  - benchmark: max_service_temp
    label: Maximum use temperature, Pyrogel XTE
    value: 650
    unit: °C
    scope: material
    conditions:
      product: Pyrogel XTE blanket
    method: Value printed on the Pyrogel XTE technical data page
    status: ground
    source: aerogel-uk-pyrogel-xte
    where: Technical data section, Max. Use Temp.
  - benchmark: density
    label: Bulk density, Stardust flight-spare silica aerogel
    value: 0.01
    unit: g/cm3
    scope: material
    conditions:
      form: Stardust flight-spare low-density silica aerogel
      note: stated as approximately
    method: Value in the abstract of an NTRS record for a Stardust interstellar dust capture study
    status: ground
    source: stardust-ntrs-2014
    where: Abstract, aerogel density
  - benchmark: thermal_conductivity
    label: Thermal conductivity, Pyrogel XTE blanket at 0 °C
    value: 20
    unit: mW/(m·K)
    scope: material
    conditions:
      temperature: 0 °C
      product: Pyrogel XTE blanket
      load: 2 psi pre-load (datasheet footnote)
    method: ASTM C177, as printed in the manufacturer datasheet table (mean temperature)
    status: ground
    source: aspen-pyrogel-xte-datasheet
    where: Thermal Conductivity table, mean temperature 32 °F / 0 °C (printed 0.14 BTU-in/hr-ft²-°F = 20 mW/m-K)
  - benchmark: thermal_conductivity
    label: Thermal conductivity, Pyrogel XTE blanket at 200 °C
    value: 28
    unit: mW/(m·K)
    scope: material
    conditions:
      temperature: 200 °C
      product: Pyrogel XTE blanket
      load: 2 psi pre-load (datasheet footnote)
    method: ASTM C177, as printed in the manufacturer datasheet table (mean temperature)
    status: ground
    source: aspen-pyrogel-xte-datasheet
    where: Thermal Conductivity table, mean temperature 392 °F / 200 °C
  - benchmark: thermal_conductivity
    label: Thermal conductivity, Pyrogel XTE blanket at 400 °C
    value: 46
    unit: mW/(m·K)
    scope: material
    conditions:
      temperature: 400 °C
      product: Pyrogel XTE blanket
      load: 2 psi pre-load (datasheet footnote)
    method: ASTM C177, as printed in the manufacturer datasheet table (mean temperature)
    status: ground
    source: aspen-pyrogel-xte-datasheet
    where: Thermal Conductivity table, mean temperature 752 °F / 400 °C
  - benchmark: thermal_conductivity
    label: Thermal conductivity, Pyrogel XTE blanket at 600 °C
    value: 89
    unit: mW/(m·K)
    scope: material
    conditions:
      temperature: 600 °C
      product: Pyrogel XTE blanket
      load: 2 psi pre-load (datasheet footnote)
    method: ASTM C177, as printed in the manufacturer datasheet table (mean temperature)
    status: ground
    source: aspen-pyrogel-xte-datasheet
    where: Thermal Conductivity table, mean temperature 1112 °F / 600 °C
  - benchmark: compressive_resistance
    label: Compressive resistance, Pyrogel XTE blanket (minimum)
    value: 3
    unit: psi
    scope: material
    conditions:
      strain: 10 % deformation
      product: Pyrogel XTE blanket
      note: printed as at least 3 psi (20.7 kPa)
    method: ASTM C165, minimum printed in the performance table
    status: ground
    source: aspen-pyrogel-xte-datasheet
    where: Performance properties table, Compressive Resistance
  - benchmark: linear_shrinkage
    label: Linear shrinkage under soaking heat, Pyrogel XTE blanket
    value: 2
    unit: '%'
    scope: material
    conditions:
      temperature: 650 °C (1200 °F) soaking heat
      product: Pyrogel XTE blanket
      note: printed as less than 2 %
    method: ASTM C356, upper bound printed in the performance table
    status: ground
    source: aspen-pyrogel-xte-datasheet
    where: Performance properties table, Linear Shrinkage Under Soaking Heat
uses:
  - application: thermal-control
    device: Lamp experiment simulating warming of the Mars surface under a silica aerogel layer
    example: A JPL article describes a lamp experiment with 2-3 centimeters of silica aerogel, which warmed the surface to up to 65 °C.
    source: nasa-jpl-colonize-mars
    where: Article text on the lamp experiment
  - application: rovers-and-surface-systems
    device: SiO2 aerogel composite insulation layer in the Mars rover
    example: "A 2025 review says the aerogel composite was used as an insulation layer in the Mars rover, which let it withstand temperatures below -100 °C."
    source: pmc12113059-aerogel-review
    where: "Aerospace section, Mars rover paragraph and its Figure 9 caption"
documents:
  - title: Technical data - Pyrogel XTE (Aspen Aerogels, reproduced by aerogel.uk.com)
    type: datasheet
    url: http://www.aerogel.uk.com/pyrogel-xte.html
  - title: Stardust Interstellar Preliminary Examination IX (NASA NTRS)
    type: report
    url: https://ntrs.nasa.gov/citations/20160004949
    year: 2014
  - title: Pyrogel XTE Product Data Sheet, Rev 4.2 (Aspen Aerogels)
    type: datasheet
    url: https://www.aerogel.com/wp-content/uploads/2021/06/Pyrogel-XTE-Datasheet-English-v4.2.pdf
    year: 2023
  - title: Investigation of the moisture induced degradation of the thermal properties of Aerogel blankets (Lakatos, Energy and Buildings)
    type: paper
    url: https://dea.lib.unideb.hu/dea/bitstream/2437/234306/1/FILE_UP_0_1-s2.0-S0378778816316589-main.pdf
    year: 2017
  - title: Mechanical Properties of Aerogels (NASA NTRS 19960016728)
    type: report
    url: https://ntrs.nasa.gov/citations/19960016728
    year: 1995
  - title: Silicon, Mineral Commodity Summaries 2026 (USGS)
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf
    year: 2026
  - title: PubChem CID 24261, Silica
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/24261
  - title: 'Silica Aerogel: Synthesis and Applications (Journal of Nanomaterials)'
    type: paper
    url: https://sonar.ch/global/documents/196790
    year: 2010
  - {title: "Review of Lightweight, High-Temperature Thermal Insulation Materials for Aerospace (MDPI Materials, 2025)", type: paper, url: "https://pmc.ncbi.nlm.nih.gov/articles/PMC12113059", year: 2025}
gaps:
  - 'Rover use: the JPL article and a 2025 MDPI review (PMC12113059) both say aerogel insulated the Mars rover. No primary NASA rover document was read, so the review is the only source for the rover detail.'
  - 'Stardust: no NASA page on the Stardust aerogel''s design was read. The 0.01 g/cm3 value comes from one NTRS abstract, and the NASA PDF link redirects to a page not read.'
  - 'Distributor and datasheet disagree: the distributor page prints 14 mW/(m·K) at 0 °C, the Aspen datasheet 20 mW/(m·K). Both are kept with their sources.'
  - Pyrogel XTE test standard is now read (ASTM C177 at 2 psi pre-load, footnote). Conductivity below 0 °C is not in the datasheet.
  - 'Cryogel and other Aspen grades: Cryogel Z page exists but its datasheet was not read.'
  - 'Producers: the country shares of aerogel makers were not read. IDTechEx claims about China capacity are behind a paywall. Aspen Aerogels is headquartered in Northborough, MA, USA (datasheet footer). Cabot describes continuous ambient-condition production but names no location.'
  - Supply abundance for silica or silicon was not read beyond the USGS note that the source is silica.
  - Critical-mineral listing for silicon was not checked.
  - Outgassing in vacuum, tensile strength and hydrophobicity numbers (contact angle) were not read.
  - Silica dust safety data sheet and exposure limit were not read, so no side effects of dust are sourced.
  - Compressive resistance and linear shrinkage are not in spores/property-canon.yaml; short snake_case names are used.
  - Moisture data come from building-insulation blankets wetted for up to 20 hours, not from space conditions.
sources:
  aerogel-uk-pyrogel-xte:
    title: Technical data - Pyrogel XTE (Aspen Aerogels product, reproduced by aerogel.uk.com)
    id: aerogel.uk.com Pyrogel XTE page
    url: http://www.aerogel.uk.com/pyrogel-xte.html
    kind: web
    license: distributor web page, linked not reproduced
  stardust-ntrs-2014:
    title: 'Stardust Interstellar Preliminary Examination IX: High-Speed Interstellar Dust Analog Capture in Stardust Flight-Spare Aerogel'
    id: NASA report ARC-E-DAA-TN19026; doi:10.1111/maps.12173
    url: https://ntrs.nasa.gov/citations/20160004949
    year: 2014
    kind: report
    license: NASA public document
  nasa-jpl-colonize-mars:
    title: Want to Colonize Mars? Aerogel Could Help (NASA JPL news)
    id: JPL news article
    url: https://www.jpl.nasa.gov/news/want-to-colonize-mars-aerogel-could-help/
    kind: web
    license: NASA public web page
  aspen-pyrogel-xte-datasheet:
    title: Pyrogel XTE Product Data Sheet, Rev 4.2 (Aspen Aerogels)
    id: Aspen Aerogels Rev 4.2, copyright 2023
    url: https://www.aerogel.com/wp-content/uploads/2021/06/Pyrogel-XTE-Datasheet-English-v4.2.pdf
    kind: datasheet
    year: 2023
    license: manufacturer datasheet, linked not reproduced
  aspen-pyrogel-xte-web:
    title: Pyrogel XTE product page (Aspen Aerogels)
    id: aerogel.com product page
    url: https://www.aerogel.com/product/pyrogel-xte/
    kind: web
    license: manufacturer web page, linked not reproduced
  lakatos2017:
    title: 'Investigation of the moisture induced degradation of the thermal properties of Aerogel blankets: measurements, calculations, simulations'
    id: doi:10.1016/j.enbuild.2017.01.054
    url: https://dea.lib.unideb.hu/dea/bitstream/2437/234306/1/FILE_UP_0_1-s2.0-S0378778816316589-main.pdf
    kind: paper
    year: 2017
    license: accepted manuscript in institutional repository
  parmenter-milstein-1995:
    title: Mechanical Properties of Aerogels (Parmenter and Milstein, UC Santa Barbara)
    id: NASA NTRS 19960016728
    url: https://ntrs.nasa.gov/citations/19960016728
    kind: report
    year: 1995
    license: NASA public document
  usgs-silicon-2026:
    title: Silicon, Mineral Commodity Summaries 2026 (USGS)
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf
    kind: report
    year: 2026
    license: US government public domain
  cabot-aerogel:
    title: Cabot Corporation, aerogel products page
    id: cabotcorp.com aerogel page
    url: https://www.cabotcorp.com/solutions/products-plus/aerogel
    kind: web
    license: corporate web page, linked not reproduced
  pubchem-silica:
    title: PubChem compound CID 24261, Silica (GHS classification)
    id: PubChem CID 24261
    url: https://pubchem.ncbi.nlm.nih.gov/compound/24261
    kind: database
    license: PubChem public database
  journal-nanomat-2010:
    title: 'Silica Aerogel: Synthesis and Applications'
    id: Journal of Nanomaterials, 2010
    url: https://sonar.ch/global/documents/196790
    kind: paper
    year: 2010
    license: repository copy, linked not reproduced
  pmc12113059-aerogel-review:
    title: "Review of Lightweight, High-Temperature Thermal Insulation Materials for Aerospace (Materials, MDPI, 2025)"
    id: PMC12113059
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC12113059
    year: 2025
    kind: paper
    license: Open access, as listed by PMC
license: CC-BY-4.0
updated: '2026-10-19'
story:
  why: Silica aerogel is a very low-density insulator. Pyrogel XTE has a nominal density of 200 kg/m3 and a conductivity of 14 mW/(m·K) at 0 °C.
  can_do:
    - label: Insulation
      value: 14 mW/(m·K) at 0 °C
      line: 'Insulate at cold temperatures: the Pyrogel XTE datasheet prints 20 mW/(m·K) at 0 °C, rising to 28 at 200 °C and 89 at 600 °C. A distributor reproduction of the same product prints 14 mW/(m·K) at 0 °C; the datasheet is the manufacturer source.'
    - label: Service limit
      value: 650 °C
      line: Stay in service up to 650 °C for the Pyrogel XTE grade.
    - label: Low density
      value: 0.01 g/cm3
      line: 'Collect fast particles: the Stardust flight-spare aerogel was about 0.01 g/cm3.'
  compare: Only one commercial grade is sourced here, so no comparison with other insulators is made.
  good_for:
    - Thermal blankets for Mars surface systems, where the JPL article describes insulation under a lamp experiment.
  watch_out:
    - 'Conductivity rises with temperature: 89 mW/(m·K) at 600 °C is more than four times the 20 mW/(m·K) at 0 °C in the datasheet.'
    - The datasheet values are for a fibre-batting blanket with aerogel inside, not for pure aerogel.
    - Wetting raises conductivity by about 20 to 40 %, per the Lakatos paper, which tested building blankets rather than space hardware.
  verdict: Strong insulation at low temperature, with datasheet values for one blanket grade. Moisture is the main weakness, and the rover use is now sourced to a JPL article but not to a primary rover document.
  risk_groups:
    - title: For people
      level: 0
      verdict: Not classified hazardous in most reports
      lead: PubChem lists silica as not meeting GHS hazard criteria in most company reports, but some reports give irritation codes.
      points:
        - label: The substance
          line: PubChem records 7,724 of 9,127 company reports (about 85 %) as not meeting GHS hazard criteria. Only 1,403 reports give hazard codes.
        - label: Irritation
          line: In the 2,540 reports that give a classification, the codes H315 (skin irritation), H319 (serious eye irritation) and H335 (may cause respiratory irritation) each appear in 56.3 % of the notifications. 889 of those 2,540 reports say it does not meet criteria.
        - label: Dust
          line: No safety data sheet or dust-exposure limit for silica aerogel was read in this run. Treat loose dust as an irritant until the supplier sheet says otherwise.
    - title: If it fails
      lead: The main failure mode in the sourced data is moisture.
      points:
        - label: Wetting
          line: The Lakatos paper reports that wetting raised conductivity by about 20 to 40 % over 0 to 20 hours at 90 % relative humidity.
        - label: Ageing
          line: NASA reports that ageing made the aerogel stiffer and stronger in compression, and that it broke at lower strain.
  recipe:
    line: Silica aerogel is amorphous silicon dioxide (SiO2) with air filling most of its volume. A silicon alkoxide such as TMOS or TEOS in alcohol forms a silica gel by sol-gel processing. The liquid in the gel is then removed by supercritical drying, which keeps the network from collapsing into a dense solid. The review says supercritical drying is the most common method; Wikipedia names supercritical CO2 or freeze-drying.
    parts:
      - name: Silicon
        symbol: Si
        atoms: 1
        role: Forms the silica network, a rigid solid framework of Si-O bonds.
      - name: Oxygen
        symbol: O
        atoms: 2
        role: Bridges the silicon atoms, so each unit is SiO2. The pores between the network strands are filled with air.
    source: journal-nanomat-2010
  uses:
    - where: Mars rovers
      line: NASA JPL says aerogel has been used as insulation on all of NASA's Mars rovers. It is the one space application for which this profile holds a source.
    - where: Industrial pipes and vessels
      line: The manufacturer sells Pyrogel XTE for insulating pipes, vessels and valves, and says it resists corrosion under insulation.
    - where: Lab test of Mars surface warming
      line: A lamp test with 2 to 3 cm of silica aerogel warmed the surface beneath it by up to 65 °C, according to JPL.
  compare_rows:
    - label: Thermal conductivity at 0 °C
      benchmark: thermal_conductivity
    - label: Density
      benchmark: density
    - label: Maximum use temperature
      benchmark: max_service_temp
  handling:
    - Keep the blanket dry. It is hydrophobic, but the Lakatos paper shows that wetting can raise conductivity by about 20 to 40 %.
    - The manufacturer says a Pyrogel XTE blanket can be removed and reused several times without degradation, after inspection.
    - No safety data sheet for silica aerogel was read, so dust handling is not sourced here.
corrosion:
  - environment: Wetting by liquid water or humid air (moisture uptake)
    headline: Wetting raises conductivity by about 20 to 40 %, so keep the blanket dry.
    effect: The paper reports that thermal conductivity of aerogel blankets can increase significantly, about 20 to 40 %, after wetting. Conductivity rose as the samples wetted over 0 to 20 hours at 90 % relative humidity.
    rating: moderate
    conditions:
      exposure: 0, 4, 8, 12, 16 and 20 h wetting at 293 K and 90 % relative humidity, in a climatic chamber
      material: silica aerogel blankets for building insulation (glass-fibre reinforced)
      test: heat flow meter on individual slabs
    source: lakatos2017
    where: Abstract; measurements section on wetting time
  - environment: Heating at the top service temperature (650 °C soaking heat)
    headline: Linear shrinkage stays below 2 % at 650 °C.
    effect: The datasheet prints linear shrinkage under soaking heat of less than 2 % at 1200 °F (650 °C), tested by ASTM C356. It does not give the shrinkage at other temperatures or times.
    rating: low
    conditions:
      temperature: 650 °C (1200 °F)
      standard: ASTM C356
    source: aspen-pyrogel-xte-datasheet
    where: Performance properties table
  - environment: Long storage and repeated handling (mechanical ageing)
    headline: Aged aerogel gets stiffer and stronger in compression, but breaks at lower strain.
    effect: A NASA report on silica aerogels states that aging increased compressive strength and elastic moduli and decreased strain at fracture. Desiccation, which removed trapped moisture, did not appreciably change the mechanical properties. The abstract gives no ageing times or conditions.
    rating: low
    conditions:
      material: fibre-reinforced silica aerogel
      note: magnitudes and ageing conditions not given in the abstract
    source: parmenter-milstein-1995
    where: Abstract
supply:
  - subject: Silicon metal (related commodity; the silica feedstock chain for aerogel is not covered by this table)
    abundance: Not read in this run. USGS says the silicon comes from silica in natural forms such as quartzite and that resources are abundant.
    producers:
      - country: China
        share_percent: 87
        year: 2025
        basis: 'computed: 4,000 thousand t of 4,600 thousand t world silicon metal (USGS table, 2025)'
      - country: Brazil
        share_percent: 3.9
        year: 2025
        basis: 'computed: 180 thousand t of 4,600 thousand t'
      - country: Norway
        share_percent: 2.8
        year: 2025
        basis: 'computed: 130 thousand t of 4,600 thousand t'
    supply_note: Shares are computed by the assistant from the printed tonnage and the printed world total (USGS rounds its world totals), not printed by USGS. Units are thousand metric tons of silicon content.
    critical_lists: []
    source: usgs-silicon-2026
    where: World Production table, silicon metal, 2024 and 2025; Events, Trends and Issues
review:
  status: draft
  method: assistant
  checked_values: 6
  unreachable: 1
  caveats: 3
  note: 'Deepened on 2026-10-19: six datasheet and NASA values added, each read in this run. The Stardust PDF and the IDTechEx article could not be read.'
risks:
  hazards:
    - text: PubChem records silica (CID 24261) as not meeting GHS hazard criteria in 7,724 of 9,127 company reports (about 85 %). Only 1,403 reports give hazard codes.
      ghs: []
      source: pubchem-silica
      where: GHS Classification, first aggregate block (9,127 reports)
    - text: In the 2,540 reports that give a classification, H315 (skin irritation), H319 (serious eye irritation) and H335 (may cause respiratory irritation) each appear in 56.3 % of the notifications. 889 of those 2,540 reports say it does not meet GHS criteria.
      ghs:
        - H315
        - H319
        - H335
      source: pubchem-silica
      where: GHS Classification, second aggregate block (2,540 reports)
  failure_risks:
    - mode: Moisture uptake raises conductivity
      trigger: Wetting for 0 to 20 hours at 293 K and 90 % relative humidity
      consequence: Thermal conductivity increases by about 20 to 40 % after wetting, per the paper.
      severity: moderate
      source: lakatos2017
      where: Abstract
  side_effects: []
  handling:
    - text: The manufacturer says a Pyrogel XTE blanket can be removed and reused several times without degradation, after inspection.
      source: aspen-pyrogel-xte-web
      where: Benefits, Remove and Reuse
    - text: The blanket is hydrophobic and resists liquid water, but wetting still degrades conductivity, so seal it against water.
      source: lakatos2017
      where: Abstract
  mitigations:
    - text: Use the hydrophobic blanket to keep the insulation and the asset drier, which limits the moisture-driven conductivity rise.
      source: aspen-pyrogel-xte-datasheet
      where: Advantages, first bullet