Silicon nitride Si3N4

spore: profile
id: silicon-nitride
spore_version: 0.2
family: carbide-nitride-boride-ceramics
name: Silicon nitride
abbreviation: Si3N4
role: structural ceramic
category: ceramics
type: nitrides
summary: 'Silicon nitride is a high-strength structural ceramic used in bearing elements and high-temperature components. Its reported properties depend on the forming and densification route: this profile keeps a gas-pressure-sintered grade, several legacy NIST grades, and a manufacturer bearing grade separate. The available sources show good strength and thermal-shock properties, while also documenting oxidation in hot wet oxygen and contact damage in bearing tests.'
best_for: Structural parts and bearing elements where low mass, wear resistance, high temperature capability, or thermal shock resistance matter.
weakest_at: Grade-sensitive performance and brittle contact damage; select a process and grade, and use its own design data.
identity:
  formula: Si3N4 (trisilicon tetranitride)
  cas: 12033-89-5
  source: pubchem-sin3n4
  where: Molecular Formula and CAS sections, CID 3084099
tags:
  environments:
    - launch
    - deep-space
  stresses:
    - extreme-heat
    - thermal-cycling
    - mechanical-wear
  applications:
    - propulsion-and-tanks
    - mechanisms
    - structures
properties:
  - benchmark: density
    label: Bulk density, gas-pressure-sintered SN-GP
    value: 3.18
    value_high: 3.3
    bound: range
    unit: g/cm3
    scope: material
    conditions:
      form: gas-pressure-sintered silicon nitride
      grade: SN-GP
      basis: manufacturer's test samples
      composition: 85-92 wt% Si3N4 plus 8-15 wt% RE2O3/Al2O3 blend per Qsil datasheet
    method: Determined according to DIN 623-2, as stated in footnote [1]
    status: ground
    source: qsil-sn-gp
    where: Section 2, General Properties, Bulk Density row
  - benchmark: residual_porosity
    label: Residual porosity, gas-pressure-sintered SN-GP
    value: 1
    bound: upper
    unit: '%'
    scope: material
    conditions:
      form: gas-pressure-sintered silicon nitride
      grade: SN-GP
      printed_value: < 1%
    method: Manufacturer datasheet value; the density and porosity method is identified as DIN 623-2
    status: ground
    source: qsil-sn-gp
    where: Section 2, General Properties, Residual Porosity row and footnote [1]
  - benchmark: grain_size
    label: Grain size, longitudinal direction, gas-pressure-sintered SN-GP
    value: 1
    value_high: 15
    bound: range
    unit: µm
    scope: material
    conditions:
      form: gas-pressure-sintered silicon nitride
      grade: SN-GP
      direction: longitudinal
    method: Manufacturer datasheet range
    status: ground
    source: qsil-sn-gp
    where: Section 2, General Properties, Grain Size (Longitudinal Direction) row
  - benchmark: hardness
    label: Hardness, gas-pressure-sintered SN-GP
    value: 14.5
    unit: GPa
    scope: material
    conditions:
      form: gas-pressure-sintered silicon nitride
      grade: SN-GP
      test_method_note: The datasheet footnotes [2] and [3] appear to point to each other's property labels.
    method: Manufacturer datasheet value; test-method footnote cross-references are inconsistent in the source
    status: ground
    source: qsil-sn-gp
    where: Section 3, Mechanical Properties, Hardness row
  - benchmark: compressive_strength
    label: Compressive strength, gas-pressure-sintered SN-GP
    value: 3000
    unit: MPa
    scope: material
    conditions:
      form: gas-pressure-sintered silicon nitride
      grade: SN-GP
      basis: manufacturer's test samples
    method: Manufacturer datasheet value; no test method is stated for this row
    status: ground
    source: qsil-sn-gp
    where: Section 3, Mechanical Properties, Compressive Strength row
  - benchmark: flexural_strength
    label: Bending strength (printed as “Bendig Strength”), gas-pressure-sintered SN-GP
    value: 670
    unit: MPa
    scope: material
    conditions:
      form: gas-pressure-sintered silicon nitride
      grade: SN-GP
      basis: manufacturer's test samples
    method: Value copied as the datasheet's bending-strength row; its [3] method footnote is cross-referenced to hardness and is not used as a test method here
    status: ground
    source: qsil-sn-gp
    where: Section 3, Mechanical Properties, Bendig Strength row
  - benchmark: weibull_modulus
    label: Weibull modulus, gas-pressure-sintered SN-GP
    value: 20
    unit: unitless
    scope: material
    conditions:
      form: gas-pressure-sintered silicon nitride
      grade: SN-GP
    method: Manufacturer datasheet value
    status: ground
    source: qsil-sn-gp
    where: Section 3, Mechanical Properties, Weibull-Modulus row
  - benchmark: fracture_toughness
    label: Fracture toughness, gas-pressure-sintered SN-GP
    value: 6.2
    unit: MPa·m1/2
    scope: material
    conditions:
      form: gas-pressure-sintered silicon nitride
      grade: SN-GP
    method: Calculated from crack length derived from Vickers hardness indentation, according to Niihara, as stated in footnote [4]
    status: ground
    source: qsil-sn-gp
    where: Section 3, Mechanical Properties, Fracture Toughness row and footnote [4]
  - benchmark: elastic_modulus
    label: Young's modulus, gas-pressure-sintered SN-GP
    value: 290
    unit: GPa
    scope: material
    conditions:
      form: gas-pressure-sintered silicon nitride
      grade: SN-GP
    method: Manufacturer datasheet value
    status: ground
    source: qsil-sn-gp
    where: Section 3, Mechanical Properties, Youngs Modulus row
  - benchmark: poissons_ratio
    label: Poisson ratio, gas-pressure-sintered SN-GP
    value: 0.26
    unit: '-'
    scope: material
    conditions:
      form: gas-pressure-sintered silicon nitride
      grade: SN-GP
    method: Manufacturer datasheet value
    status: ground
    source: qsil-sn-gp
    where: Section 3, Mechanical Properties, Poisson Ratio row
  - benchmark: max_service_temp
    label: Maximum working temperature in air, gas-pressure-sintered SN-GP
    value: 1200
    unit: °C
    scope: material
    conditions:
      form: gas-pressure-sintered silicon nitride
      grade: SN-GP
      atmosphere: air
      basis: manufacturer-stated maximum working temperature
    method: Manufacturer datasheet value; not a component-specific design allowable
    status: ground
    source: qsil-sn-gp
    where: Section 4, Thermal Properties, Max. Working Temperature, Air row
  - benchmark: max_service_temp
    label: Maximum working temperature in inert atmosphere, gas-pressure-sintered SN-GP
    value: 1400
    unit: °C
    scope: material
    conditions:
      form: gas-pressure-sintered silicon nitride
      grade: SN-GP
      atmosphere: inert atmosphere
      basis: manufacturer-stated maximum working temperature
    method: Manufacturer datasheet value; not a component-specific design allowable
    status: ground
    source: qsil-sn-gp
    where: Section 4, Thermal Properties, Max. Working Temperature, Inert Atmosphere row
  - benchmark: specific_heat
    label: Specific heat capacity, gas-pressure-sintered SN-GP
    value: 620
    unit: J/kgK
    scope: material
    conditions:
      form: gas-pressure-sintered silicon nitride
      grade: SN-GP
      temperature: not stated in this row
    method: Manufacturer datasheet value
    status: ground
    source: qsil-sn-gp
    where: Section 4, Thermal Properties, Specific Heat Capacity row
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 20 °C, gas-pressure-sintered SN-GP
    value: 24
    unit: W/mK
    scope: material
    conditions:
      form: gas-pressure-sintered silicon nitride
      grade: SN-GP
      temperature: 20 °C
    method: Manufacturer datasheet value
    status: ground
    source: qsil-sn-gp
    where: Section 4, Thermal Properties, Thermal Conductivity row
  - benchmark: cte
    label: Mean coefficient of thermal expansion from room temperature to 1000 °C, gas-pressure-sintered SN-GP
    value: 3.2
    unit: 10-6K-1
    scope: material
    conditions:
      form: gas-pressure-sintered silicon nitride
      grade: SN-GP
      temperature_range: RT-1000 °C
      printed_unit: 10-6 K-1
    method: Manufacturer datasheet value, in the unit printed
    status: ground
    source: qsil-sn-gp
    where: Section 4, Thermal Properties, Coeff. of Thermal Expansion, RT-1000 °C row
  - benchmark: cte
    label: Coefficient of thermal expansion near room temperature, gas-pressure-sintered SN-GP
    value: 1.4
    unit: 10-6K-1
    scope: material
    conditions:
      form: gas-pressure-sintered silicon nitride
      grade: SN-GP
      temperature_range: RT ± 20 °C
      printed_unit: 10-6 K-1
    method: Manufacturer datasheet value, in the unit printed
    status: ground
    source: qsil-sn-gp
    where: Section 4, Thermal Properties, Coeff. of Thermal Expansion, RT ± 20 °C row
  - benchmark: thermal_shock_parameter_r1
    label: Thermal shock parameter R1, gas-pressure-sintered SN-GP
    value: 534
    unit: K
    scope: material
    conditions:
      form: gas-pressure-sintered silicon nitride
      grade: SN-GP
      test_case: critical temperature difference for infinite heat transfer (quenching)
    method: Manufacturer datasheet value; parameter definition is given in footnote [5]
    status: ground
    source: qsil-sn-gp
    where: Section 4, Thermal Properties, Thermal Shock Parameter R1 row and footnote [5]
  - benchmark: thermal_shock_parameter_r2
    label: Thermal shock parameter R2, gas-pressure-sintered SN-GP
    value: 12822
    unit: W/m
    scope: material
    conditions:
      form: gas-pressure-sintered silicon nitride
      grade: SN-GP
      test_case: finite constant heat transfer (slow heating)
    method: Manufacturer datasheet value; parameter definition is given in footnote [6]
    status: ground
    source: qsil-sn-gp
    where: Section 4, Thermal Properties, Thermal Shock Parameter R2 row and footnote [6]
  - benchmark: density
    label: Density, hot-pressed NCX-34
    value: 3.37
    unit: g cm-3
    scope: material
    conditions:
      form: hot-pressed silicon nitride
      grade: NCX-34
      temperature: not stated in NIST record
    method: Manufacturer's indicated value, reproduced in NIST Structural Ceramics Database
    status: ground
    source: nist-scd-z00426
    where: Material 1, NCX-34 specification and Density (mass) section
  - benchmark: elastic_modulus
    label: Elastic modulus, hot-pressed NCX-34
    value: 310
    unit: GPa
    scope: material
    conditions:
      form: hot-pressed silicon nitride
      grade: NCX-34
      temperature: not stated in NIST record
    method: Manufacturer's indicated value, reproduced in NIST Structural Ceramics Database
    status: ground
    source: nist-scd-z00426
    where: Material 1, NCX-34 specification and Elastic Modulus section
  - benchmark: fracture_toughness
    label: Fracture toughness, hot-pressed NCX-34
    value: 6.35
    unit: MPa m1/2
    scope: material
    conditions:
      form: hot-pressed silicon nitride
      grade: NCX-34
      uncertainty: ± 0.10 MPa m1/2
    method: Surface crack in flexure test; unevaluated in the NIST record
    status: ground
    source: nist-scd-z00426
    where: Material 1, Fracture Toughness section
  - benchmark: density
    label: Density, hot-isostatically pressed NBD200
    value: 3.16
    unit: g cm-3
    scope: material
    conditions:
      form: hot-isostatically pressed silicon nitride
      grade: NBD200
      temperature: not stated in NIST record
    method: Manufacturer's indicated value, reproduced in NIST Structural Ceramics Database
    status: ground
    source: nist-scd-z00426
    where: Material 2, NBD200 specification and Density (mass) section
  - benchmark: elastic_modulus
    label: Elastic modulus, hot-isostatically pressed NBD200
    value: 320
    unit: GPa
    scope: material
    conditions:
      form: hot-isostatically pressed silicon nitride
      grade: NBD200
      temperature: not stated in NIST record
    method: Manufacturer's indicated value, reproduced in NIST Structural Ceramics Database
    status: ground
    source: nist-scd-z00426
    where: Material 2, NBD200 specification and Elastic Modulus section
  - benchmark: fracture_toughness
    label: Fracture toughness, hot-isostatically pressed NBD200
    value: 5.41
    unit: MPa m1/2
    scope: material
    conditions:
      form: hot-isostatically pressed silicon nitride
      grade: NBD200
      uncertainty: ± 0.24 MPa m1/2
    method: Surface crack in flexure test; unevaluated in the NIST record
    status: ground
    source: nist-scd-z00426
    where: Material 2, Fracture Toughness section
  - benchmark: density
    label: Density, sintered EC-141
    value: 3.22
    unit: g cm-3
    scope: material
    conditions:
      form: sintered silicon nitride
      grade: EC-141
      temperature: not stated in NIST record
    method: Manufacturer's indicated value, reproduced in NIST Structural Ceramics Database
    status: ground
    source: nist-scd-z00426
    where: Material 5, EC-141 specification and Density (mass) section
  - benchmark: elastic_modulus
    label: Elastic modulus, sintered EC-141
    value: 310
    unit: GPa
    scope: material
    conditions:
      form: sintered silicon nitride
      grade: EC-141
      temperature: not stated in NIST record
    method: Manufacturer's indicated value, reproduced in NIST Structural Ceramics Database
    status: ground
    source: nist-scd-z00426
    where: Material 5, EC-141 specification and Elastic Modulus section
  - benchmark: fracture_toughness
    label: Fracture toughness, sintered EC-141
    value: 5.22
    unit: MPa m1/2
    scope: material
    conditions:
      form: sintered silicon nitride
      grade: EC-141
      uncertainty: ± 0.18 MPa m1/2
    method: Surface crack in flexure test; unevaluated in the NIST record
    status: ground
    source: nist-scd-z00426
    where: Material 5, Fracture Toughness section
  - benchmark: density
    label: Density, reaction-bonded NC-350
    value: 2.53
    unit: g cm-3
    scope: material
    conditions:
      form: reaction-bonded silicon nitride
      grade: NC-350
      temperature: not stated in NIST record
    method: Manufacturer's indicated value, reproduced in NIST Structural Ceramics Database
    status: ground
    source: nist-scd-z00426
    where: Material 6, NC-350 specification and Density (mass) section
  - benchmark: elastic_modulus
    label: Elastic modulus, reaction-bonded NC-350
    value: 180
    unit: GPa
    scope: material
    conditions:
      form: reaction-bonded silicon nitride
      grade: NC-350
      temperature: not stated in NIST record
    method: Manufacturer's indicated value, reproduced in NIST Structural Ceramics Database
    status: ground
    source: nist-scd-z00426
    where: Material 6, NC-350 specification and Elastic Modulus section
  - benchmark: fracture_toughness
    label: Fracture toughness, reaction-bonded NC-350
    value: 1.65
    unit: MPa m1/2
    scope: material
    conditions:
      form: reaction-bonded silicon nitride
      grade: NC-350
      uncertainty: ± 0.09 MPa m1/2
    method: Surface crack in flexure test; unevaluated in the NIST record
    status: ground
    source: nist-scd-z00426
    where: Material 6, Fracture Toughness section
  - benchmark: flexural_strength
    label: Flexural strength (MOR) at 20 °C, NBD-200
    value: 900
    unit: MPa
    scope: material
    conditions:
      form: hot-isostatically pressed silicon nitride
      grade: NBD-200
      temperature: 20 °C
    method: CoorsTek material table; the page does not state a test standard
    status: ground
    source: coorstek-sn
    where: Properties table, Flexural Strength, MOR (20 °C) row, NBD-200 column; NIST identifies the NBD200 process as hot isostatic pressing
  - benchmark: fracture_toughness
    label: Fracture toughness, NBD-200
    value: 5.5
    unit: MPa m1/2
    scope: material
    conditions:
      form: hot-isostatically pressed silicon nitride
      grade: NBD-200
    method: CoorsTek material table; the page does not state a test method
    status: ground
    note: The older NIST record for NBD200 gives 5.41 ± 0.24 MPa m1/2; the sources do not explain the difference.
    source: coorstek-sn
    where: Properties table, Fracture Toughness row, NBD-200 column; process identified in NIST entry Z00426, Material 2
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 20 °C, NBD-200
    value: 29
    unit: W/m K
    scope: material
    conditions:
      form: hot-isostatically pressed silicon nitride
      grade: NBD-200
      temperature: 20 °C
    method: CoorsTek material table; the page does not state a test method
    status: ground
    source: coorstek-sn
    where: Properties table, Thermal Conductivity (20 °C) row, NBD-200 column; process identified in NIST entry Z00426, Material 2
  - benchmark: cte
    label: Coefficient of thermal expansion, NBD-200
    value: 2.9
    unit: 1x10-6/°C
    scope: material
    conditions:
      form: hot-isostatically pressed silicon nitride
      grade: NBD-200
      printed_unit: 1x10-6/°C
    method: CoorsTek material table; unit and value copied as printed
    status: ground
    source: coorstek-sn
    where: Properties table, Coefficient of Thermal Expansion row, NBD-200 column; process identified in NIST entry Z00426, Material 2
  - benchmark: max_service_temp
    label: Maximum use temperature, NBD-200
    value: 1400
    unit: °C
    scope: material
    conditions:
      form: hot-isostatically pressed silicon nitride
      grade: NBD-200
      atmosphere: not stated on CoorsTek table
    method: Manufacturer-stated maximum use temperature; atmosphere and test method are not stated
    status: ground
    source: coorstek-sn
    where: Properties table, Maximum Use Temperature row, NBD-200 column; process identified in NIST entry Z00426, Material 2
corrosion:
  - environment: Hot oxygen containing water vapor
    headline: Water vapor increases passive oxidation of hot-pressed silicon nitride.
    effect: The review says silicon nitride forms a protective silica scale in oxidation, but its oxidation depends on sintering aids and impurities. For hot-pressed HS-130, the reported parabolic oxidation rate is higher in wet oxygen than in dry oxygen.
    rating: unknown
    conditions:
      form: hot-pressed silicon nitride, grade HS-130
      atmosphere: oxygen with water vapor; see Table 22 for the reported partial pressure
    source: biscay-oxidation
    where: Section 3.1, Oxidation of Si3N4; Section 3.2, Si3N4 in Hot Gases; Table 22
risks:
  hazards:
    - text: The PubChem aggregate for silicon nitride lists the majority of company GHS reports as not meeting hazard criteria, while noting that reports can differ with impurities, additives, and other factors.
      ghs: []
      source: pubchem-sin3n4
      where: Safety and Hazards, GHS Classification, CID 3084099
    - text: The MilliporeSigma SDS for Aldrich product 334103 (powder) classifies it as not a hazardous substance or mixture and lists no hazards otherwise classified. This is product-specific and does not establish handling requirements for every powder or finished ceramic.
      ghs: []
      source: sigma-sds-sin3n4
      where: Sections 1-2
  failure_risks:
    - mode: Brittle contact damage in cryogenic bearings
      trigger: NASA tests with silicon nitride rolling elements in 57-mm high-pressure oxidizer turbopump bearings
      consequence: The report describes spalling, striations, locally deformed ball material, and possible scuffing. It says the cause of spalling was not known and discusses a material flaw or high rolling-contact stress as possibilities.
      source: nasa-tm103524
      where: Introduction and Test Results, report pages 1-2 (PDF pages 5-6)
  side_effects: []
  handling:
    - text: For powder handling, the SDS advises avoiding dust formation and breathing dust, using exhaust ventilation where dust forms, and keeping the container tightly closed in a dry, well-ventilated place.
      source: sigma-sds-sin3n4
      where: Sections 6-7
    - text: The SDS recommends appropriate eye protection and gloves for the product powder. Use the SDS for the exact grade and process; these instructions are not a substitute for supplier guidance on machining dust.
      source: sigma-sds-sin3n4
      where: Section 8
  mitigations: []
uses:
  - application: mechanisms
    device: Rolling elements in cryogenic turbopump bearings
    example: NASA evaluated silicon nitride balls in flight-type Space Shuttle Main Engine high-pressure oxidizer turbopump bearings. The report describes a test program, not a claim that the tested configuration flew.
    source: nasa-tm103524
    where: Introduction and Test Equipment, report page 1 (PDF page 5)
  - application: propulsion-and-tanks
    device: Aerospace propulsion and control components
    example: CoorsTek lists propulsion and control components among its silicon nitride aerospace and defense applications.
    source: coorstek-sn
    where: Sample Applications by Industry, Aerospace & Defense
  - application: mechanisms
    device: High-temperature bearings
    example: PubChem's sources/uses section lists high-temperature ball bearings among reported uses for silicon nitride.
    source: pubchem-sin3n4
    where: Use and Manufacturing, Sources/Uses
supply:
  - subject: Silicon feedstock for silicon nitride; the USGS report does not report silicon nitride production
    abundance: The USGS says world and domestic resources for silicon metal and alloys are abundant and names silica, including quartzite, as the source. Its narrative estimates China at almost 80% of global silicon materials production in 2025. The producer shares below are computed from the report's separate 2025 silicon-metal production column; they describe feedstock, not silicon nitride output.
    producers:
      - country: China
        share_percent: 87
        year: 2025
      - country: Brazil
        share_percent: 3.9
        year: 2025
      - country: Norway
        share_percent: 2.8
        year: 2025
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (elemental silicon feedstock)
        listed: true
    recycling: Not reported for silicon nitride in the sources read.
    substitutes: []
    source: usgs-mcs2026-silicon
    where: 'Events, Trends, and Issues; World Production; World Resources; critical-minerals discussion. Computed silicon-metal shares: China 4,000/4,600 = 87%, Brazil 180/4,600 = 3.9%, Norway 130/4,600 = 2.8% (2025 column, kt).'
documents:
  - title: Material Data Sheet for Gas Pressure Sintered Silicon Nitride, SN-GP, Revision 07
    type: datasheet
    url: https://qsil.com/wp-content/uploads/2023/04/F_4-4_26_Material-Data-Sheet-SN-GP.pdf
    year: 2022
  - title: Silicon Nitride material page, CoorsTek
    type: datasheet
    url: https://www.coorstek.com/en/materials/silicon-nitride/
  - title: NIST Structural Ceramics Database, Citation Z00426
    type: database
    url: https://srdata.nist.gov/CeramicDataPortal/Scd/Z00426
  - title: NASA TM-103524, An Evaluation of Bearings Operating in a Cryogenic Environment with Silicon Nitride Rolling Elements
    type: report
    url: https://ntrs.nasa.gov/api/citations/19910009123/downloads/19910009123.pdf
    year: 1991
  - title: USGS Mineral Commodity Summaries 2026, Silicon
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf
    year: 2026
  - title: PubChem Compound Summary, Trisilicon tetranitride (CID 3084099), PUG-View record
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/3084099/JSON
    year: 2026
  - title: CIAAW 2024 Abridged Standard Atomic Weights
    type: database
    url: https://www.ciaaw.org/abridged-atomic-weights.htm
    year: 2024
  - title: Corrosion Characteristics of Silicon Carbide and Silicon Nitride, Journal of Research of NIST
    type: paper
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC4907592/
    year: 1993
  - title: MilliporeSigma Safety Data Sheet, Silicon nitride, Aldrich 334103, Version 6.3
    type: sds
    url: https://sds.mcmaster.ca/Silicon_Nitride.pdf
    year: 2022
gaps:
  - USGS does not report silicon-nitride producer shares or output; the supply section is explicitly silicon feedstock context.
  - The exact rare-earth oxide/alumina proportions and rare-earth identity in the SN-GP sintering-aid blend are not specified by the datasheet.
  - The Qsil datasheet's footnotes [2] and [3] appear cross-referenced to the opposite property labels, so those test methods could not be confidently assigned to hardness and bending strength.
  - No tensile strength values were found for the specific SN-GP, NIST, or NBD-200 grades in the sources read; the 670 MPa Qsil value is labeled as bending strength, and CoorsTek labels its values as flexural MOR.
  - The hot-gas oxidation evidence read here is for hot-pressed HS-130; corrosion of every listed grade in other gases, molten salts, and chemical environments remains uncharacterized in this profile.
  - The Sigma SDS applies to one laboratory powder product; finished ceramic and machining-dust guidance for each manufacturer grade was not found.
  - NIST's legacy material values and current CoorsTek NBD-200 values differ for fracture toughness; the sources do not explain the difference, so the entries remain separate.
  - Maximum working/use temperatures are supplier table values; component-specific lifetime, atmosphere, geometry, and design allowables were not established by the sources read.
sources:
  qsil-sn-gp:
    title: Qsil, Material Data Sheet for Gas Pressure Sintered Silicon Nitride, SN-GP, Revision 07
    id: F_4-4_26, dated 2022-01-18
    url: https://qsil.com/wp-content/uploads/2023/04/F_4-4_26_Material-Data-Sheet-SN-GP.pdf
    year: 2022
    kind: datasheet
    license: Manufacturer datasheet, linked and cited
  coorstek-sn:
    title: CoorsTek Technical Ceramics, Silicon Nitride material page and grade table
    url: https://www.coorstek.com/en/materials/silicon-nitride/
    kind: datasheet
    license: Manufacturer webpage, cited
  nist-scd-z00426:
    title: NIST Structural Ceramics Database, Citation Z00426, silicon nitride entries
    url: https://srdata.nist.gov/CeramicDataPortal/Scd/Z00426
    kind: database
    license: Public domain (NIST), cited
  nasa-tm103524:
    title: NASA TM-103524, An Evaluation of Bearings Operating in a Cryogenic Environment with Silicon Nitride Rolling Elements
    id: NTRS 19910009123
    url: https://ntrs.nasa.gov/api/citations/19910009123/downloads/19910009123.pdf
    year: 1991
    kind: report
    license: Public domain (NASA), cited
  usgs-mcs2026-silicon:
    title: USGS Mineral Commodity Summaries 2026, Silicon
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf
    year: 2026
    kind: report
    license: Public domain (USGS), cited
  pubchem-sin3n4:
    title: PubChem PUG-View record, Trisilicon tetranitride (CID 3084099)
    id: CID 3084099; CAS 12033-89-5
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/3084099/JSON
    year: 2026
    kind: database
    license: Public domain (NCBI), cited
  ciaaw-atomic-weights:
    title: Commission on Isotopic Abundances and Atomic Weights, 2024 Abridged Standard Atomic Weights
    url: https://www.ciaaw.org/abridged-atomic-weights.htm
    year: 2024
    kind: database
    license: CIAAW reference table, cited
  biscay-oxidation:
    title: Corrosion Characteristics of Silicon Carbide and Silicon Nitride, Journal of Research of NIST
    id: PMCID PMC4907592
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC4907592/
    year: 1993
    kind: paper
    license: Publicly accessible NIST journal review, cited
  sigma-sds-sin3n4:
    title: MilliporeSigma Safety Data Sheet, Silicon nitride, Aldrich 334103, Version 6.3
    id: Revision 25 April 2022; CAS 12033-89-5
    url: https://sds.mcmaster.ca/Silicon_Nitride.pdf
    year: 2022
    kind: datasheet
    license: Supplier safety data sheet, linked and cited
license: CC-BY-4.0
updated: '2026-10-20'
review:
  status: draft
  method: assistant
  checked_values: 35
  unreachable: 0
  caveats: 4
  note: Each property is tied to a named grade and form. The Qsil bending/hardness footnotes and the two NBD-200 fracture-toughness entries are flagged in the profile.
story:
  recipe:
    line: 'The compound formula is Si3N4: three silicon atoms and four nitrogen atoms, with CIAAW 2024 abridged standard atomic weights of 28.085 and 14.007 respectively. Qsil''s gas-pressure-sintered SN-GP grade reports 85 to 92 wt% Si3N4 and 8 to 15 wt% combined RE2O3/Al2O3 sintering aids; the sheet does not split that blend further.'
    parts:
      - name: Silicon nitride matrix
        symbol: Si3N4
        share_percent: 85
        share_high: 92
        role: The main ceramic phase in the SN-GP grade.
        source: qsil-sn-gp
        where: Section 2, Chemical Composition, Si3N4 (wt.-%) row
      - name: Silicon
        symbol: Si
        atoms: 3
        atomic_weight: 28.085
        role: Three silicon atoms in each Si3N4 formula unit.
        source: ciaaw-atomic-weights
        where: 2024 Abridged Standard Atomic Weights, silicon row; atom count from the Si3N4 formula in PubChem CID 3084099
      - name: Nitrogen
        symbol: 'N'
        atoms: 4
        atomic_weight: 14.007
        role: Four nitrogen atoms in each Si3N4 formula unit.
        source: ciaaw-atomic-weights
        where: 2024 Abridged Standard Atomic Weights, nitrogen row; atom count from the Si3N4 formula in PubChem CID 3084099
      - name: RE2O3/Al2O3 sintering-aid blend
        share_percent: 8
        share_high: 15
        role: Combined oxide additions reported for the SN-GP grade; exact blend is not specified.
        source: qsil-sn-gp
        where: Section 2, Chemical Composition, RE2O3/Al2O3 (wt.-%) row
  risk_groups:
    - title: For people
      level: 1
      verdict: Powder SDS not classified
      lead: The powder SDS read here says the named product is not hazardous under its GHS classification, and still gives dust-control and personal-protection instructions.
      points:
        - label: Powder handling
          line: Avoid dust generation and inhalation; use the handling instructions on the SDS for the exact powder product.
    - title: If a bearing part fails
      lead: A NASA cryogenic test report documents contact damage and leaves its cause unresolved.
      points:
        - label: Contact damage
          line: The report describes spalling, striations, deformed ball areas, and possible scuffing in tested silicon nitride bearing balls.
    - title: Hot gas exposure
      lead: Oxidation varies with the sintering aids and impurities, and water vapor can increase it in hot oxygen.
      points:
        - label: Oxidation
          line: A review describes formation of a protective silica scale but cautions that scale behavior depends on composition and environment.
  why: Silicon nitride is a structural ceramic whose elongated grains and intergranular phases can give it useful strength and toughness. It appears in bearing elements and aerospace propulsion components, where wear, heat, and thermal shock matter. Processing changes density and fracture behavior substantially, so a material name alone is not a design specification.
  uses:
    - where: Cryogenic turbopump bearings
      line: NASA evaluated silicon nitride rolling elements in Space Shuttle Main Engine high-pressure oxidizer turbopump bearings; the cited report describes ground testing.
    - where: Aerospace propulsion and control
      line: CoorsTek lists silicon nitride propulsion and control components as an aerospace and defense application.
    - where: High-temperature bearings
      line: PubChem's sources/uses record lists high-temperature ball bearings among reported uses for silicon nitride.
  can_do:
    - label: Carry bending loads
      benchmark: flexural_strength
      line: Datasheets report bending or flexural strength for named grades; the test mode is explicitly kept distinct from tensile strength.
    - label: Limit thermal shock
      benchmark: thermal_shock_parameter_r1
      line: The Qsil SN-GP sheet reports thermal-shock parameters for separate heating and quenching cases.
    - label: Conduct heat
      benchmark: thermal_conductivity
      line: The Qsil and CoorsTek data give grade-specific thermal conductivity, and the values should be compared only with their listed forms.
  compare: The data show why silicon nitride needs a form and grade attached to every value. Qsil's SN-GP gas-pressure-sintered grade, NIST's hot-isostatically pressed and sintered records, and the reaction-bonded NC-350 record are separate materials for comparison purposes. The fracture-toughness entries for NBD-200 also differ between the older NIST record and the current CoorsTek table, with no explanation in either source.
  compare_rows:
    - label: Density by process and grade
      benchmark: density
    - label: Flexural or bending strength by grade
      benchmark: flexural_strength
    - label: Fracture toughness by process and grade
      benchmark: fracture_toughness
  handling:
    - 'For powder, follow the exact supplier SDS: avoid dust, use ventilation where dust forms, and keep the container dry and closed.'
    - Do not transfer a bulk property table directly to a component with a different shape, surface, or processing route; the Qsil sheet explicitly limits its data to test samples.
    - For hot oxygen environments, account for oxidation and water-vapor effects; the available study is limited to a hot-pressed grade.
  good_for:
    - Bearing elements and propulsion hardware where wear resistance and temperature capability matter.
    - Applications needing low thermal expansion and resistance to thermal shock, provided the selected grade has relevant design data.
  watch_out:
    - Do not combine values from reaction-bonded, sintered, hot-pressed, and gas-pressure-sintered forms as though they were one grade.
    - The Qsil sheet's hardness and bending-strength method footnotes are ambiguous, and the NBD-200 toughness values differ between sources.
    - No grade-specific tensile strength or silicon-nitride production share was found in the sources read.
  verdict: Silicon nitride suits demanding bearings and structural parts when its exact grade and processing route are specified. The profile has a strong set of sourced values, including thermal and mechanical data, while the method ambiguity in one datasheet and limited grade-specific oxidation and supply information remain visible.