Molybdenum disilicide MoSi2

spore: profile
id: molybdenum-disilicide
spore_version: 0.2
family: carbide-nitride-boride-ceramics
name: Molybdenum disilicide
abbreviation: MoSi2
role: high-temperature electric heating element material (dense silicide cermet, sold as Kanthal Super)
category: ceramics
type: ultra-high-temperature-ceramics
summary: |
  Molybdenum disilicide is a dense cermet of MoSi2 with a mainly glass phase, sold as Kanthal Super heating elements. Kanthal's datasheets give a density of 5.6 g/cm3 for Super 1700 and 6.5 g/cm3 for Super 1900, a bending strength of 450 MPa at 20 degC, a Vickers hardness of 9 GPa and a fracture toughness of 3 to 4 MPa·m1/2. The maximum operating temperature in air is 1700 degC for Super 1700 and 1850 degC for Super 1900. The material forms a quartz-glass layer that protects it from oxidation, but Kanthal says it is brittle below about 1200 degC, and surface oxidation near 500 degC gives a yellowish MoO3 powder. NACA measured room-temperature electrical resistivity at 23 to 27 microohm-cm in 1952. Molybdenum, one of its two elements, is produced mostly in China, Chile, the United States, Peru and Mexico (USGS 2026).
best_for: Electric heating elements in air furnaces for heat treatment, forging, sintering and glass melting, at element temperatures up to about 1700 to 1850 degC
weakest_at: Brittleness below about 1200 degC (Kanthal), and low-temperature oxidation near 500 degC that forms yellowish MoO3 powder
identity:
  formula: MoSi2
  cas: 12136-78-6
  source: pubchem-mosi2
  where: PubChem CID 6336985 record (MolecularFormula MoSi2, MolecularWeight 152.12). CAS 12136-78-6 from Section 3 of the Stanford Advanced Materials SDS (stanford-sds).
tags:
  environments: []
  stresses:
    - extreme-heat
  applications:
    - in-space-manufacturing
    - structures
properties:
  - benchmark: density
    label: Density, Kanthal Super 1700
    value: 5.6
    unit: g/cm3
    scope: material
    conditions:
      grade: Kanthal Super 1700
      printed: 5.6 (0.20) g/cm3 (lbs/in3)
    method: Physical properties table, density row, Kanthal Super 1700 datasheet (updated 2010-05-11)
    status: ground
    source: kanthal-super-1700
    where: Physical properties table, Density row
  - benchmark: density
    label: Density, Kanthal Super 1900
    value: 6.5
    unit: g/cm3
    scope: material
    conditions:
      grade: Kanthal Super 1900
      printed: 6.5 (0.23) g/cm3
    method: Physical properties table, density row, Kanthal Super 1900 product page
    status: ground
    note: The Kanthal handbook prints 6.5 g/cm3 for the 'other Kanthal Super' column, which is not the same table as the Super 1700 datasheet (5.6 g/cm3). Both are kept with their grade.
    source: kanthal-super-1900
    where: Physical properties table, Density row
  - benchmark: density
    label: Relative density (supplier SDS)
    value: 6.31
    unit: g/mL
    scope: material
    conditions:
      temperature: 25 degC
      grade: not stated
    method: Relative density in Section 9 of the supplier SDS, printed as 6.31 g/mL at 25 degC (numerically equal to g/cm3)
    status: ground
    note: Supplier SDS value; grade and form are not stated in the SDS.
    source: stanford-sds
    where: Section 9, Relative density
  - benchmark: max_service_temp
    label: Maximum operating temperature in air, Kanthal Super 1700
    value: 1700
    unit: degC
    scope: material
    conditions:
      atmosphere: air
      grade: Kanthal Super 1700
    method: Last row of the Super 1700 physical properties table
    status: ground
    source: kanthal-super-1700
    where: Physical properties table, Maximum operating temperature in air row
  - benchmark: max_service_temp
    label: Maximum operating temperature in air, Kanthal Super 1900
    value: 1850
    unit: degC
    scope: material
    conditions:
      atmosphere: air
      grade: Kanthal Super 1900
    method: Maximum operating temperature in air row, Kanthal Super 1900 product page
    status: ground
    source: kanthal-super-1900
    where: Physical properties table, Maximum operating temperature in air row
  - benchmark: hardness
    label: Vickers hardness HV, Kanthal Super 1700 and 1900
    value: 9
    unit: GPa
    scope: material
    conditions:
      temperature: 20 degC
      basis: HV value printed for Super 1700; the same value is printed on the Super 1900 product page
    method: Hardness HV row of the mechanical properties table
    status: ground
    source: kanthal-super-1700
    where: Mechanical properties table, Hardness HV row
  - benchmark: flexural_strength
    label: Bending strength, Kanthal Super 1700 and 1900
    value: 450
    unit: MPa
    scope: material
    conditions:
      temperature: 20 degC
      grade: Kanthal Super 1700 (Super 1900 page prints the same value)
    method: Bending strength row of the mechanical properties table
    status: ground
    source: kanthal-super-1700
    where: Mechanical properties table, Bending strength row
  - benchmark: compressive_strength
    label: Compression strength, Kanthal Super (all grades except ER and HT in the table)
    value: 1400
    value_high: 1500
    bound: range
    unit: MPa
    scope: material
    conditions:
      temperature: 20 degC
      grade: Kanthal Super family, handbook table column for other grades
    method: Compression strength row of the Kanthal Super mechanical and physical properties table (handbook)
    status: ground
    source: kanthal-handbook
    where: Table 'The mechanical and physical properties of Kanthal Super', Compression strength row
  - benchmark: fracture_toughness
    label: Fracture toughness KIC, Kanthal Super 1700
    value: 3
    value_high: 4
    bound: range
    unit: MPa·m1/2
    scope: material
    conditions:
      temperature: 20 degC
      grade: Kanthal Super 1700
    method: Fracture toughness KIC row of the mechanical properties table, printed as 3-4 MPa√m
    status: ground
    source: kanthal-super-1700
    where: Mechanical properties table, Fracture toughness KIC row
  - benchmark: ultimate_tensile_strength
    label: Tensile strength at 1500 degC, Kanthal Super 1700 and 1900
    value: 100
    unit: MPa
    scope: material
    conditions:
      temperature: 1500 degC (2820 degF)
      grade: Kanthal Super 1700 datasheet and Super 1900 page
    method: Tensile strength at elevated temperatures table
    status: ground
    note: The handbook prints 100 MPa +/- 25 percent at 1550 degC for another group of grades. The temperatures differ, so both rows are kept.
    source: kanthal-super-1700
    where: Tensile strength at elevated temperatures table, 1500 (2820) row
  - benchmark: ultimate_tensile_strength
    label: Tensile strength at 1550 degC, Kanthal Super HT and other grades (handbook)
    value: 100
    unit: MPa
    scope: material
    conditions:
      temperature: 1550 degC (2820 degF)
      tolerance: +/- 25 percent
      grade: Kanthal Super HT and other grades in the handbook table
    method: Tensile strength at 1550 degC row of the Kanthal Super mechanical and physical properties table
    status: ground
    source: kanthal-handbook
    where: Table 'The mechanical and physical properties of Kanthal Super', Tensile strength row
  - benchmark: thermal_conductivity
    label: Thermal conductivity, 20 to 600 degC
    value: 30
    unit: W/m·K
    scope: material
    conditions:
      temperature: 20 to 600 degC (68 to 1110 degF)
      grade: Kanthal Super 1700
    method: Thermal conductivity row, first temperature band
    status: ground
    source: kanthal-super-1700
    where: Physical properties table, Thermal conductivity row, 20-600 degC column
  - benchmark: thermal_conductivity
    label: Thermal conductivity, 600 to 1200 degC
    value: 15
    unit: W/m·K
    scope: material
    conditions:
      temperature: 600 to 1200 degC (1110 to 2190 degF)
      grade: Kanthal Super 1700
    method: Thermal conductivity row, second temperature band
    status: ground
    source: kanthal-super-1700
    where: Physical properties table, Thermal conductivity row, 600-1200 degC column
  - benchmark: cte
    label: Coefficient of linear expansion, Kanthal Super 1700
    value: 7
    value_high: 8
    bound: range
    unit: 10-6/K
    scope: material
    conditions:
      temperature: not stated in the datasheet row
      grade: Kanthal Super 1700
    method: Coefficient of linear expansion row, printed as 7-8 10-6/K
    status: ground
    source: kanthal-super-1700
    where: Physical properties table, Coefficient of linear expansion row
  - benchmark: specific_heat
    label: Specific heat capacity, Kanthal Super 1700
    value: 0.42
    unit: kJ/kg·K
    scope: material
    conditions:
      temperature: 20 degC (68 degF)
      grade: Kanthal Super 1700
    method: Specific heat capacity at 20 degC row
    status: ground
    source: kanthal-super-1700
    where: Physical properties table, Specific heat capacity row
  - benchmark: porosity
    label: Porosity, Kanthal Super 1700
    value: 1
    bound: upper
    unit: '%'
    scope: material
    conditions:
      grade: Kanthal Super 1700
    method: Porosity row, printed as less than 1 percent
    status: ground
    source: kanthal-super-1700
    where: Physical properties table, Porosity row
  - benchmark: emissivity
    label: Emissivity, Kanthal Super 1700
    value: 0.7
    value_high: 0.8
    bound: range
    unit: '-'
    scope: material
    conditions:
      grade: Kanthal Super 1700
    method: Emissivity row, printed as 0.70-0.80
    status: ground
    source: kanthal-super-1700
    where: Physical properties table, Emissivity row
  - benchmark: electrical_resistivity
    label: Electrical resistivity at room temperature, MoSi2 (NACA 1952)
    value: 23
    value_high: 27
    bound: range
    unit: uOhm·cm
    scope: material
    conditions:
      temperature: room temperature
      basis: depends on the method of fabrication; NACA printed microhm-centimeters
    method: Summary, third paragraph; the memo says the conductivity is metallic and decreases with temperature up to 2000 degF
    status: ground
    source: naca-rm-e52a04
    where: Summary, third paragraph
  - benchmark: elastic_modulus
    label: Modulus of elasticity at room temperature, MoSi2 (NACA 1952, dynamic method)
    value: 59
    unit: psi x 10^6
    scope: material
    conditions:
      temperature: room temperature
      method_detail: dynamic method
    method: Summary, fourth paragraph; printed as 59 x 10^6 pounds per square inch. Kept in the printed unit, so the importer converts it. The memo also says poor damping characteristics at room temperature.
    status: ground
    source: naca-rm-e52a04
    where: Summary, third paragraph
  - benchmark: ignition_temperature
    label: Ignition temperature of MoSi2 powder in air
    value: 405
    value_high: 510
    bound: range
    unit: degF
    scope: material
    conditions:
      form: powder
      basis: small samples rapidly heated in a furnace; 510 degF for 3.0 g and 405 degF for 20.0 g
    method: Results, Oxidation of powdered MoSi2, first paragraph
    status: ground
    note: Custom property name. Powder property, not a bulk property.
    source: naca-rm-e52a04
    where: Results, Oxidation of powdered MoSi2, first paragraph
corrosion:
  - environment: Air at about 500 degC (930 degF), low-temperature oxidation (pest)
    headline: Molybdenum and silicon on the surface oxidise to a yellowish MoO3 powder. The handbook says this normally has no detrimental effect.
    effect: Kanthal says oxidation of molybdenum and silicon on the surface of the elements can occur at temperatures around 500 degC (930 degF). The product is a yellowish powder, MoO3, which normally has no detrimental effect on performance. In the separate note on aluminised elements, the handbook adds that pest under the aluminising means the temperature has been far too high.
    rating: low
    conditions:
      temperature: about 500 degC (930 degF)
      atmosphere: air
    source: kanthal-handbook
    where: Section 'Air' under the atmosphere guidance, and the note on loose contacts and pest
  - environment: Air at high temperature (protective quartz-glass layer)
    headline: A thin quartz-glass layer forms on the surface, protecting the material up to the rated element temperature.
    effect: Kanthal says Super elements withstand oxidation at high temperature because a thin, adhesive protective layer of quartz glass forms on the surface. NACA (1952) identified the protective coating on oxidised MoSi2 as cristobalite. Kanthal's datasheet calls the material resistant to corrosion and oxidation.
    rating: low
    conditions:
      temperature: up to 1700 to 1850 degC element temperature in air (Super 1700 and 1900)
      atmosphere: air
    source: kanthal-handbook
    where: Introduction page, text on oxidation resistance (THIS IS KANTHAL SUPER)
  - environment: Furnace atmospheres containing water vapour or carbon dioxide
    headline: Water vapour and carbon dioxide act as oxidising agents. The size of the effect is not given in the part read.
    effect: The handbook states that water vapour and carbon dioxide in any amount in the atmosphere have an oxidising effect. The rest of the atmosphere guidance was not reviewed in this pass, so no rate or temperature limit is given here.
    rating: unknown
    conditions:
      atmosphere: furnace atmosphere containing water vapour or carbon dioxide
    source: kanthal-handbook
    where: Atmosphere guidance, 'Water vapor and carbon dioxide' paragraph
risks:
  hazards:
    - text: 'PubChem aggregated GHS for molybdenum disilicide (CID 6336985, signal word Warning): H302 (74.5 percent of reports), H312 (74.5 percent) and H332 (74.5 percent). 25.5 percent (13 of 51 reports) say the substance does not meet GHS hazard criteria.'
      ghs:
        - H302
        - H312
        - H332
      source: pubchem-mosi2
      where: Safety and Hazards, GHS Classification
    - text: 'Supplier SDS (Stanford Advanced Materials, revised 04/02/2023): acute toxicity category 4 by oral, dermal and inhalation routes; H302 + H312 + H332 harmful if swallowed, in contact with skin or if inhaled; signal word Warning.'
      ghs:
        - H302
        - H312
        - H332
      source: stanford-sds
      where: Section 2, GHS Classification and Label elements
  failure_risks:
    - mode: Brittle fracture below about 1200 degC
      trigger: Mechanical load or thermal stress on an element operated below about 1200 degC
      consequence: Kanthal says the material is more brittle at lower temperatures and becomes ductile around 1200 degC. The Super 1700 datasheet gives a bending strength of 450 MPa and a fracture toughness of 3 to 4 MPa·m1/2 at 20 degC.
      severity: moderate
      source: kanthal-super-1700
      where: Mechanical properties table; Introduction page (ductile at about 1200 degC)
    - mode: Element failure from carbon build-up in a carburising furnace
      trigger: High carbon potential in a carburising atmosphere, with element temperature normally kept below 1400 degC
      consequence: Kanthal says that carbon build-up in the furnace can lead to element failure, and recommends regular removal of the carbon by firing the furnace under oxidising conditions.
      severity: moderate
      source: kanthal-handbook
      where: Section 'Carburizing atmosphere'
  side_effects: []
  handling:
    - text: 'Powder: NACA (1952) says that in powdered form MoSi2 is not inherently resistant to oxidation and burns in air at comparatively low temperatures. Ignition temperatures were 510 degF (3.0 g sample) and 405 degF (20.0 g sample). A 5-pound quantity held at 212 degF overnight oxidised completely.'
      source: naca-rm-e52a04
      where: Results, Oxidation of powdered MoSi2, first paragraph
    - text: 'Powder dust: the supplier SDS says to avoid dust formation, to avoid breathing dust and to provide exhaust ventilation where dust is formed.'
      source: stanford-sds
      where: Section 7 (handling) and Section 8 (exposure controls)
    - text: PubChem lists H302, H312 and H332 for the compound. Avoid swallowing it, skin contact and breathing the dust.
      source: pubchem-mosi2
      where: Safety and Hazards, GHS Classification
  mitigations:
    - text: Kanthal recommends keeping the element temperature normally below 1400 degC in carburising furnaces, and removing carbon build-up regularly by firing the furnace under oxidising conditions.
      source: kanthal-handbook
      where: Section 'Carburizing atmosphere'
uses:
  - application: in-space-manufacturing
    device: Electric heating elements for industrial furnaces (heat treatment, forging, sintering and glass melting)
    example: Kanthal says typical application for Super 1700 includes most types of industrial furnace for heat treatment, forging, sintering, glass melting and refining, and for radiant tubes. This is a terrestrial furnace use; the application tag is the nearest item in the list, and no space furnace use was read.
    source: kanthal-super-1700
    where: Introduction page, 'Typical area of application' paragraph
  - application: structures
    device: Oxidation-protective silicide coatings on molybdenum (research only)
    example: NACA (1952) says silicon-containing coatings, which appear to derive their oxidation resistance from the presence of MoSi2, offer considerable promise for protecting molybdenum at high temperatures. This is a research statement, not a production use.
    source: naca-rm-e52a04
    where: Introduction, second paragraph
supply:
  - subject: Molybdenum (the molybdenum half of MoSi2)
    abundance: 'USGS: identified molybdenum resources are about 5.4 million tons in the United States and about 20 million tons in the rest of the world, and are adequate to supply world needs for the foreseeable future. World reserves are 17,000 thousand tons (2025, as printed).'
    producers:
      - country: China
        share_percent: 37.3
        year: 2025
      - country: Chile
        share_percent: 16.2
        year: 2025
      - country: United States
        share_percent: 15.4
        year: 2025
      - country: Peru
        share_percent: 15
        year: 2025
      - country: Mexico
        share_percent: 6.5
        year: 2025
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (final list of 60 minerals; molybdenum is not on it)
        listed: false
      - list: EU critical raw materials list (Regulation (EU) 2024/1252, European Commission page; molybdenum is not in the list read)
        listed: false
    recycling: 'USGS: molybdenum is recycled as a component of catalysts, ferrous scrap and superalloy scrap.'
    substitutes:
      - 'USGS: potential substitutes for refractory materials in high-temperature electric furnaces are graphite, tantalum and tungsten.'
    source: usgs-mcs2026-molybdenum
    where: World Mine Production and Reserves table, 2025e column (world total 260,000 t, rounded; shares calculated by Space Mushroom as country output over that total); Events, Trends and Issues (China export controls on molybdenum powders, February 2025); Recycling; Substitutes
  - subject: Silicon (the silicon half of MoSi2, as silicon metal)
    abundance: 'USGS: China accounted for almost 80 percent of total global estimated production of silicon materials (ferrosilicon and silicon metal) in 2025. Silicon metal world production in 2025 was 4,600 thousand tons (rounded, as printed).'
    producers:
      - country: China
        share_percent: 87
        year: 2025
      - country: Brazil
        share_percent: 3.9
        year: 2025
      - country: Norway
        share_percent: 2.8
        year: 2025
      - country: France
        share_percent: 1.5
        year: 2025
      - country: Australia
        share_percent: 1
        year: 2025
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (silicon added in the final 2025 list)
        listed: true
      - list: EU critical raw materials list (Regulation (EU) 2024/1252, silicon metal, European Commission page)
        listed: true
    recycling: 'USGS: insignificant.'
    substitutes:
      - 'USGS: gallium arsenide and germanium are the principal substitutes for silicon in semiconductor and infrared applications. No substitute for silicon in MoSi2 is discussed.'
    source: usgs-mcs2026-silicon
    where: World Production table, silicon metal 2025 column (world total 4,600 thousand tons, rounded; shares calculated by Space Mushroom); Events, Trends and Issues; critical minerals paragraph; Recycling; Substitutes
media: []
documents:
  - title: Kanthal Super 1700 (Molybdenum disilicide) datasheet, copy hosted on ibt.co.il, updated 2010-05-11
    type: datasheet
    url: https://www.ibt.co.il/uploaded_files/documents/datasheet-kanthal-super-1700_U1212.pdf
    year: 2010
  - title: Kanthal Super 1900 product datasheet page (kanthal.com)
    type: datasheet
    url: https://kanthal.com/en/products/material-datasheets/ceramic-elements/molybdenum-disilicide/kanthal-super-1900
    year: 2026
  - title: Kanthal Super electric heating elements handbook (English)
    type: datasheet
    url: https://prodshop.kanthal.com/globalassets/kanthal-global/downloads/super-handbook_b_eng.pdf
  - title: Maxwell, W. A., NACA RM E52A04, Oxidation-Resistance Mechanism and Other Properties of Molybdenum Disilicide (1952)
    type: report
    url: https://ntrs.nasa.gov/api/citations/19930086994/downloads/19930086994.pdf
    year: 1952
  - title: Stanford Advanced Materials, Safety Data Sheet, Molybdenum Silicide (MoSi2), revised 04/02/2023
    type: sds
    url: https://samaterials.com/tds/1697120333-803-molybdenum-silicide-evaporation-materials-sds.pdf
    year: 2023
  - title: PubChem compound record CID 6336985, molybdenum disilicide (GHS classification)
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/6336985
    year: 2026
  - title: USGS Mineral Commodity Summaries 2026, Molybdenum
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-molybdenum.pdf
    year: 2026
  - title: USGS Mineral Commodity Summaries 2026, Silicon
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf
    year: 2026
gaps:
  - Melting point not found in this pass. The OSTI record for the Kanthal-era review (2030 degC in a search snippet) was not readable, and the DTIC report returned an error page. No melting value is in the file.
  - Crystal system and space group not found in this pass, so identity has no crystal_system or space_group.
  - 'Designations: only the trade-name family ''Kanthal Super'' is printed in a source read in this run. UNS, EN, DIN, JIS and AISI codes were not found. The Super grades 1700, 1800, 1900, HT, RA and ER are different grades and are not listed as designations.'
  - 'Density conflict: 5.6 g/cm3 (Super 1700 datasheet), 6.5 g/cm3 (Super 1900 page and the handbook''s other-grades column), 7.0 g/cm3 (Super HT, handbook) and 6.31 g/mL (supplier SDS, grade not stated). All are kept with their grade or source.'
  - 'Tensile strength temperature conflict: the Super 1700 datasheet prints 100 MPa at 1500 degC, the handbook prints 100 MPa +/- 25 percent at 1550 degC for other grades. Both are kept.'
  - Super HT grade (bending strength 350 to 400 MPa, density 7.0 g/cm3, porosity below 1 percent) is in the handbook but not included, because the file covers the Super 1700 and 1900 grades.
  - 'Pest (low-temperature oxidation) window: only ''around 500 degC'' is printed by the handbook. The McKamey and Meschter papers on pest oxidation (Cambridge and scholarhub.vn abstracts) were paywalled or not readable, so no pest temperature range or rate is recorded.'
  - Open-access MoSi2 review or paper giving a melting point, hardness at temperature, or oxidation rates was not opened in this run. The MDPI Materials 2026 article (doi 10.3390/ma19081653) returned HTTP 403 and the Torino repository copy returned an HTML page, so neither is used.
  - 'Custom property names used because they are not in spores/property-canon.yaml: hardness, compressive_strength, fracture_toughness, porosity, emissivity, ignition_temperature.'
  - 'Space use: no NASA, ESA or flight source for MoSi2 heating elements or coatings was read. The NACA 1952 memo is laboratory research. No vacuum, radiation or atomic-oxygen data were read.'
  - Hazard data rest on the PubChem aggregate and one supplier SDS. The SDS lists no melting point, and its toxicology section was not checked in this run.
  - 'Supply shares: molybdenum shares are calculated against the rounded 260,000 t world total (country values sum to 259,900 t). Silicon shares are calculated against the rounded 4,600 thousand t silicon-metal total. Both are Space Mushroom calculations, not USGS figures.'
  - The EU critical raw materials page read does not explicitly confirm the annex contents of Regulation (EU) 2024/1252. Molybdenum is absent and silicon metal is listed on the page read.
  - Crustal abundance of molybdenum and silicon not found in this pass.
  - The NACA memo sentence pairs the two ignition temperatures (510 degF and 405 degF) with the 3.0 g and 20.0 g samples in order, and that order is used here.
sources:
  kanthal-super-1700:
    title: Kanthal Super 1700 (Molybdenum disilicide) datasheet, updated 2010-05-11
    url: https://www.ibt.co.il/uploaded_files/documents/datasheet-kanthal-super-1700_U1212.pdf
    kind: datasheet
    license: Kanthal datasheet, copy hosted on ibt.co.il; cited, not reproduced
  kanthal-super-1900:
    title: Kanthal Super 1900, material datasheet page (kanthal.com)
    url: https://kanthal.com/en/products/material-datasheets/ceramic-elements/molybdenum-disilicide/kanthal-super-1900
    kind: datasheet
    license: Kanthal product page; cited, not reproduced
  kanthal-handbook:
    title: Kanthal Super electric heating elements handbook (English, super-handbook_b_eng.pdf)
    url: https://prodshop.kanthal.com/globalassets/kanthal-global/downloads/super-handbook_b_eng.pdf
    kind: handbook
    license: Kanthal handbook; cited, not reproduced
  naca-rm-e52a04:
    title: Maxwell, W. A., Oxidation-Resistance Mechanism and Other Properties of Molybdenum Disilicide, NACA RM E52A04 (1952)
    url: https://ntrs.nasa.gov/api/citations/19930086994/downloads/19930086994.pdf
    kind: report
    license: public domain (NASA NTRS)
  stanford-sds:
    title: Stanford Advanced Materials, Safety Data Sheet, Molybdenum Silicide (MoSi2), revised 04/02/2023
    url: https://samaterials.com/tds/1697120333-803-molybdenum-silicide-evaporation-materials-sds.pdf
    kind: datasheet
    license: supplier document, linked not reproduced
  pubchem-mosi2:
    title: PubChem compound CID 6336985, molybdenum disilicide (GHS classification, aggregated notifications)
    url: https://pubchem.ncbi.nlm.nih.gov/compound/6336985
    kind: database
    license: PubChem public database
  pubchem-mo:
    title: PubChem compound CID 23932, molybdenum (MolecularFormula Mo, MolecularWeight 95.95)
    url: https://pubchem.ncbi.nlm.nih.gov/compound/23932
    kind: database
    license: PubChem public database
  pubchem-si:
    title: PubChem compound CID 5461123, silicon (MolecularFormula Si, MolecularWeight 28.085)
    url: https://pubchem.ncbi.nlm.nih.gov/compound/5461123
    kind: database
    license: PubChem public database
  usgs-mcs2026-molybdenum:
    title: USGS Mineral Commodity Summaries 2026, Molybdenum
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-molybdenum.pdf
    kind: report
    license: US government work, public domain
  usgs-mcs2026-silicon:
    title: USGS Mineral Commodity Summaries 2026, Silicon
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf
    kind: report
    license: US government work, public domain
  usgs-critical-2025:
    title: About the 2025 List of Critical Minerals (USGS, final list of 60 minerals)
    url: https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals
    kind: web
    license: public domain (USGS)
  ec-crm:
    title: Critical raw materials (European Commission, list under Regulation (EU) 2024/1252)
    url: https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en
    kind: web
    license: European Commission web page
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 20
  unreachable: 3
  caveats: 6
  note: 'Written in this run from the Kanthal Super 1700 datasheet, the Kanthal Super 1900 page, the Kanthal handbook, NACA RM E52A04 (1952), the Stanford Advanced Materials SDS, PubChem CID 6336985, USGS MCS 2026 molybdenum and silicon, the USGS 2025 critical-minerals page and the European Commission list page. Not reachable: OSTI 364016 (connection refused), DTIC AD0408003 (error page), the MDPI Materials 2026 article (403) and the Springer pest-oxidation paper (paywall redirect). verify-values: 20 of 20 values found in their cited sources.'
story:
  recipe:
    line: MoSi2 has one molybdenum atom and two silicon atoms per formula unit (PubChem, MolecularFormula MoSi2). NACA made the compound by combining the elements directly, grinding the raw material in water, then leaching it with acids and caustic and drying it in vacuum. Kanthal's commercial element is a dense cermet of MoSi2 with an oxide component, mainly a glass phase.
    parts:
      - name: Molybdenum
        symbol: Mo
        atoms: 1
        atomic_weight: 95.95
        role: The metal atom in the compound. Molybdenum and silicon together form the MoSi2 phase that gives the element its high-temperature strength and conductivity.
      - name: Silicon
        symbol: Si
        atoms: 2
        atomic_weight: 28.085
        role: Forms the protective quartz-glass layer on the surface, which is what protects the element against oxidation in air at high temperature.
  risk_groups:
    - title: For people
      level: 0
      verdict: Harmful if swallowed, in contact with skin or if inhaled…
      lead: Both the PubChem aggregate and a supplier SDS give H302, H312 and H332 with the signal word Warning. PubChem also records that 25.5 percent of reports say the substance does not meet GHS criteria. The supplier SDS lists no melting point.
      points:
        - label: Dust
          line: The supplier SDS says to avoid dust formation and to provide exhaust ventilation where dust is formed.
        - label: Powder
          line: NACA (1952) found that powdered MoSi2 burns in air at comparatively low temperatures, with ignition at 405 and 510 degF depending on sample size.
    - title: If an element fails
      lead: These points come from Kanthal's datasheets and handbook, and from the 1952 NACA memo.
      points:
        - label: Brittleness
          line: Kanthal says the material is brittle below about 1200 degC and becomes ductile around that temperature. Bending strength is 450 MPa at 20 degC.
        - label: Low-temperature oxidation
          line: Around 500 degC the surface can oxidise to a yellowish MoO3 powder. Kanthal says this normally does not harm performance.
        - label: Carburising furnaces
          line: Carbon build-up in the furnace can lead to element failure. Kanthal recommends regular removal by firing under oxidising conditions.
  why: Molybdenum disilicide is a silicide cermet used for electric heating elements in high-temperature air furnaces. Its surface forms a quartz-glass layer that resists oxidation, so the element can run at up to about 1700 to 1850 degC according to Kanthal's grade table. The same material is brittle at lower temperatures, so element handling and the temperature band both matter. The sources read here give a bending strength of 450 MPa, a density of 5.6 to 6.5 g/cm3 depending on grade, and a room-temperature electrical resistivity of 23 to 27 microohm-cm (NACA 1952).
  uses:
    - where: Industrial furnaces
      line: Kanthal says Super 1700 elements are used in most types of industrial furnace for heat treatment, forging, sintering, glass melting and refining, and in radiant tubes.
    - where: Oxidation-protective coatings (research)
      line: NACA (1952) reported that silicon-containing coatings, which derive their oxidation resistance from MoSi2, look promising for protecting molybdenum at high temperature. This is a research finding, not a production use.
    - where: Space applications
      line: No flight, space or lunar source for MoSi2 heating elements was read in this run.
  can_do:
    - label: Heat in air
      benchmark: max_service_temp
      value: 1850 degC
      line: Kanthal gives a maximum operating temperature in air of 1700 degC for Super 1700 and 1850 degC for Super 1900.
    - label: Stiffness
      benchmark: elastic_modulus
      line: NACA (1952) measured a room-temperature modulus of elasticity of 59 x 10^6 psi by a dynamic method. It also notes poor damping at room temperature.
    - label: Hardness
      benchmark: hardness
      value: 9 GPa
      line: Kanthal gives a Vickers hardness HV of 9 GPa for Super 1700 and Super 1900.
    - label: Heat conduction
      benchmark: thermal_conductivity
      value: 30 W/m·K
      line: Kanthal gives 30 W/m·K from 20 to 600 degC and 15 W/m·K from 600 to 1200 degC for Super 1700.
  compare: No other heating-element material was read in this run, so this profile does not rank MoSi2 against silicon carbide, FeCrAl or other furnace materials. Within this profile, Super 1700 has a density of 5.6 g/cm3 and a maximum operating temperature in air of 1700 degC, and Super 1900 has a density of 6.5 g/cm3 and 1850 degC.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Maximum operating temperature in air
      benchmark: max_service_temp
    - label: Thermal conductivity
      benchmark: thermal_conductivity
  handling:
    - 'Powder: PubChem lists H302, H312 and H332 for the compound. Avoid swallowing it, skin contact and breathing the dust.'
    - 'Powder ignition: NACA found that the powder ignites in air at 405 to 510 degF, depending on sample size, and that a 5-pound quantity held at 212 degF oxidised completely overnight.'
    - 'Furnace: keep carburising-furnace element temperature normally below 1400 degC and remove carbon build-up by firing under oxidising conditions (Kanthal).'
  good_for:
    - High-temperature furnace elements in air. Kanthal gives a maximum operating temperature in air of 1700 degC (Super 1700) and 1850 degC (Super 1900).
    - Hard, stiff ceramic parts at room temperature. Kanthal gives a Vickers hardness of 9 GPa and NACA gives a modulus of 59 x 10^6 psi.
  watch_out:
    - Brittleness below about 1200 degC. Kanthal gives a bending strength of 450 MPa and a fracture toughness of 3 to 4 MPa·m1/2 at 20 degC.
    - Low-temperature oxidation near 500 degC, which forms yellowish MoO3 powder.
    - Density differs by grade, from 5.6 g/cm3 (Super 1700 datasheet) to 6.5 g/cm3 (Super 1900 page). Use the grade's own datasheet.
    - No space, radiation or vacuum data were read.
  verdict: Molybdenum disilicide is a high-temperature furnace heating-element material. It is rated to 1700 to 1850 degC in air and protects itself with a quartz-glass layer, but it is brittle below about 1200 degC and its powder ignites at low temperature. The sourced uses are terrestrial industrial furnaces, and no space application was found.