spore: profile
id: silicon-monoxide
spore_version: 0.2
family: oxide-ceramics
name: Silicon monoxide
abbreviation: SiO
role: evaporation source for thin oxide films and lithium-ion anode material
category: ceramics
type: oxides
summary: |
  Silicon monoxide (SiO) is a black, water-insoluble solid with a melting point of 1702 °C and a density of 2.13 g/cc, as printed in two supplier safety data sheets. Solid SiO is used as an evaporation source for SiO films in optical coatings. As a lithium-ion anode it is a high-capacity material: the Xiamen review puts the reversible capacity of commercial SiO at 1300 to 1700 mAh/g, but it also reports a volume change of about 200% on cycling and a low first-cycle Coulombic efficiency. The space record is for a related SiOx coating: a 1000 Å film on aluminised Kapton flew on LDEF for 10 months, eroded uniformly, and its integrated solar absorptance moved from 0.363 (unflown control) to 0.391 (flown).
best_for: Thin SiO films for optical coatings, and a high-capacity lithium-ion anode where cycle life can be traded (the review describes the capacity; cycle life is the open problem)
weakest_at: Volume change and first-cycle lithium loss in an anode (about 200% volume change, low initial Coulombic efficiency); the space test covers a SiOx coating, not bulk SiO
identity:
  formula: SiO
  cas: 10097-28-6
  source: pubchem-sio
  where: PubChem CID 66241, Silicon oxide (SiO); CAS 10097-28-6 printed in Section 1.1 of the SPI Supplies SDS and Section 1 of the Angstrom Sciences SDS; EC number 233-232-8 in the Angstrom Sciences SDS, Section 1
tags:
  environments:
    - low-earth-orbit
  stresses:
    - atomic-oxygen
  applications:
    - thermal-control
    - batteries
    - optics-and-cameras
properties:
  - benchmark: density
    label: Density, SiO chips (Angstrom Sciences SDS)
    value: 2.13
    unit: g/cc
    scope: material
    conditions:
      grade: SiO, 100 wt% (supplier SDS, Section 3)
      form: powder, granules, pellets or sputtering target
    method: Value printed in a supplier safety data sheet
    status: ground
    source: angstrom-sds
    where: Section 9, Density row
  - benchmark: melting_point
    label: Melting point, SiO chips (SPI Supplies SDS)
    value: 1702
    unit: °C
    scope: material
    conditions:
      grade: SPI-Chem SiO chips, 3 to 6 mm
      pressure: not stated
    method: Value printed in a supplier safety data sheet
    status: ground
    note: The Stanford Advanced Materials SDS prints 1702.00 °C too. ChemicalBook gives 1870 °C, which is not used because it was not read from a source opened for this profile.
    source: twospi-sds
    where: Section 9.1, Freezing/Melting Point row
  - benchmark: melting_point
    label: Melting point, SiO (Stanford Advanced Materials SDS)
    value: 1702
    unit: °C
    scope: material
    conditions:
      grade: silicon monoxide, 100% (SDS Section II)
    method: Value printed in a supplier safety data sheet
    status: ground
    source: sam-sds
    where: Section III, Melting Point row
  - benchmark: melting_point
    label: Melting point lower bound, SiO (Angstrom Sciences SDS)
    value: 1702
    bound: lower
    unit: °C
    scope: material
    conditions:
      grade: silicon monoxide, 100 wt%
    method: Printed as a greater-than value in a supplier safety data sheet
    status: ground
    source: angstrom-sds
    where: Section 9, Melting Point row
  - benchmark: boiling_point
    label: Boiling point, SiO (PubChem experimental record)
    value: 1880
    unit: °C
    scope: material
    conditions:
      pressure: 760 mm Hg
      basis: experimental value in the PubChem record
    method: Experimental value quoted in a chemical database
    status: ground
    source: pubchem-sio
    where: Chemical and Physical Properties, Experimental Properties, Boiling Point
  - benchmark: boiling_point
    label: Boiling point, SiO chips (SPI Supplies SDS)
    value: 1880
    unit: °C
    scope: material
    conditions:
      grade: SPI-Chem SiO chips, 3 to 6 mm
    method: Value printed in a supplier safety data sheet
    status: ground
    source: twospi-sds
    where: Section 9.1, Boiling Point row (also printed as 3416.0 °F)
  - benchmark: solar_absorptance
    label: Solar absorptance, 1000 Å SiOx on aluminised Kapton, flown on LDEF
    value: 0.391
    unit: '-'
    scope: material
    conditions:
      coating: 1000 Å SiOx deposited on the vacuum-deposited aluminium face of Kapton (sample 3)
      exposure: LDEF ram-facing tray, low Earth orbit, 10 months
      measurement: integrated reflectance of the flown sample
    method: Integrated value printed in a NASA report after spectrophotometer measurement
    status: flight
    note: SiOx, not pure SiO. The flown value is compared with the unflown control in the next entry.
    source: nasa-ldef-1995
    where: Section 4, Radiative Analysis for the 1000 Å SiOx sample; Figure 11
  - benchmark: solar_absorptance
    label: Solar absorptance, 1000 Å SiOx on Kapton, unflown control
    value: 0.363
    unit: '-'
    scope: material
    conditions:
      coating: 1000 Å SiOx on the vacuum-deposited aluminium face of Kapton
      reference: unflown reference sample kept for comparison
    method: Integrated value printed in a NASA report
    status: ground
    source: nasa-ldef-1995
    where: Section 4, Radiative Analysis for the 1000 Å SiOx sample
  - benchmark: thermal_emittance
    label: Thermal emittance, 1000 Å SiOx on Kapton, flown on LDEF
    value: 0.547
    unit: '-'
    scope: material
    conditions:
      coating: 1000 Å SiOx on the vacuum-deposited aluminium face of Kapton
      exposure: LDEF ram-facing tray, low Earth orbit, 10 months
    method: Integrated value printed in a NASA report
    status: flight
    source: nasa-ldef-1995
    where: Section 4, Radiative Analysis for the 1000 Å SiOx sample
  - benchmark: thermal_emittance
    label: Thermal emittance, 1000 Å SiOx on Kapton, unflown control
    value: 0.564
    unit: '-'
    scope: material
    conditions:
      coating: 1000 Å SiOx on the vacuum-deposited aluminium face of Kapton
      reference: unflown reference sample
    method: Integrated value printed in a NASA report
    status: ground
    source: nasa-ldef-1995
    where: Section 4, Radiative Analysis for the 1000 Å SiOx sample
  - benchmark: volume_change
    value: 200
    unit: '%'
    scope: material
    conditions:
      basis: volume change of SiO during lithiation and delithiation in a lithium-ion cell
    method: Approximate value quoted in an open review (printed as about 200%)
    status: ground
    note: The review prints about 200%, and states that this breaks up and detaches the anode material.
    source: zhu2022
    where: English abstract, first paragraph
  - benchmark: specific_capacity
    label: Specific capacity quoted for SiO (review, approximate)
    value: 2043
    unit: mAh/g
    scope: material
    conditions:
      basis: figure quoted for SiO as a lithium-ion anode; the review does not call it theoretical
    method: Approximate value quoted in an open review
    status: calculated
    note: Reported as a high specific capacity, not as a theoretical value; the review gives no lithium stoichiometry for this figure.
    source: zhu2022
    where: English abstract, first paragraph
  - benchmark: practical_capacity
    label: Reversible capacity range, pure SiO (commercial materials)
    value: 1300
    value_high: 1700
    bound: range
    unit: mAh/g
    scope: material
    conditions:
      basis: reversible specific capacity from testing of commercialised SiO materials, as stated in the review
      rate: not stated in the review
    method: Range quoted in an open review
    status: ground
    note: A range from commercial materials, not from a single defined test.
    source: zhu2022
    where: English abstract, first paragraph
  - benchmark: delithiation_potential
    label: Delithiation (charge) potential, SiO anode
    value: 0.5
    bound: upper
    unit: V
    scope: material
    conditions:
      basis: stated as suitable, below 0.5 V; reference electrode not stated
    method: Value quoted in an open review
    status: ground
    source: zhu2022
    where: English abstract, first paragraph
corrosion:
  - environment: Atomic oxygen in low Earth orbit (ram-facing tray on LDEF, 10 months)
    headline: A 1000 Å SiOx film on aluminised Kapton eroded uniformly and changed little in radiative properties.
    effect: The NASA report says the 1000 Å SiOx coating eroded uniformly, with minor changes in its radiative properties. Its integrated absorptance went from 0.363 (unflown control) to 0.391 (flown), and its emittance from 0.564 to 0.547.
    rating: low
    conditions:
      coating: SiOx, 1000 Å, on vacuum-deposited aluminium on Kapton
      exposure: LDEF ram-facing position, low Earth orbit, 10 months
      note: A coating result for SiOx; no bulk SiO was flown
    source: nasa-ldef-1995
    where: Summary; Section 4, Radiative Analysis for the 1000 Å SiOx sample; Section 5 (Conclusions)
  - environment: Lithium-ion anode, first discharge and charge
    headline: Lithium silicate and lithium oxide form irreversibly in the first cycle and use up lithium.
    effect: The review says lithium silicate and lithium oxide are irreversibly formed during the initial discharge and charge of SiO, which lowers the initial Coulombic efficiency and limits long-term cycling.
    rating: moderate
    conditions:
      cell: lithium-ion cell with an SiO anode, as reviewed
      note: A review statement; no first-cycle efficiency for pure SiO is quoted
    source: zhu2022
    where: English abstract, first paragraph
risks:
  hazards:
    - text: PubChem reports that silicon monoxide does not meet GHS hazard criteria in 0.9% (3 of 327) of company reports. The rest classify it as a skin irritant (H315, 97.9%), a serious eye irritant (H319, 97.9%) and a single-exposure respiratory irritant (H335, 66.1%), with the signal word Warning.
      ghs:
        - H315
        - H319
        - H335
      source: pubchem-sio
      where: Safety and Hazards, GHS Classification (CID 66241)
    - text: The SPI Supplies SDS (effective January 2018) states that the product is not a hazardous substance or mixture and carries no GHS label elements. The Angstrom Sciences SDS (2015) lists no signal word and no hazard statements.
      ghs: []
      source: twospi-sds
      where: Sections 2.1 and 2.2; Angstrom Sciences SDS, Section 2
    - text: The Stanford Advanced Materials SDS lists skin and eye redness and abrasive irritation, and says that inhalation may cause respiratory irritation. It also lists chronic inhalation effects of pneumoconiosis, pulmonary fibrosis and silicosis, but cites no test for SiO.
      ghs: []
      source: sam-sds
      where: Section VI, Health Hazards (Acute and Chronic)
  failure_risks:
    - mode: Volume change and pulverisation of an SiO anode
      trigger: Lithiation and delithiation of SiO in a lithium-ion cell
      consequence: The review says the volume change of about 200% can pulverise the anode and cause the material to detach, which damages the interface and the cycle life.
      severity: high
      source: zhu2022
      where: English abstract, first paragraph
    - mode: Irreversible lithium loss in the first cycle
      trigger: First discharge and charge of an SiO anode
      consequence: Lithium silicate and lithium oxide form irreversibly, which lowers the initial Coulombic efficiency and limits long-term cycling.
      severity: moderate
      source: zhu2022
      where: English abstract, first paragraph
    - mode: Low electrical conductivity of the anode
      trigger: Use of bulk SiO without conductive treatment
      consequence: The review gives the conductivity of SiO as relatively low, and links it to a low initial Coulombic efficiency and poor long-term cycling.
      severity: moderate
      source: zhu2022
      where: English abstract, first paragraph
    - mode: Erosion of a thin SiOx film in low Earth orbit
      trigger: Atomic oxygen on an unprotected SiOx film, 10 months on LDEF
      consequence: The 1000 Å coating eroded uniformly and kept its optical behaviour within a small change, so the film thinned without the failure seen in some other coatings in the same test.
      severity: low
      source: nasa-ldef-1995
      where: Summary; Section 5 (Conclusions)
  side_effects: []
  handling:
    - text: Store in a cool, dry area, in a tightly closed container, as the SPI Supplies SDS advises.
      source: twospi-sds
      where: Section 7.2 (Conditions for safe storage)
    - text: Use local exhaust where dust forms and avoid breathing dust. The SDS gives a TLV of 10 mg/m3 and an OSHA PEL of 15 mg/m3 for total dust.
      source: twospi-sds
      where: Section 8.1 (Workplace exposure limits) and Section 8.2.1
    - text: Keep away from strong oxidising agents, strong acids and strong bases.
      source: twospi-sds
      where: Section 10.5 (Incompatible materials)
  mitigations:
    - text: Wear a NIOSH approved dust respirator where dust is generated, and use safety glasses and impervious gloves.
      source: sam-sds
      where: Section VIII, Protective Equipment Summary
    - text: A N95 or P1 dust mask is advised where nuisance dust is a concern, and NIOSH or CEN approved respirators where conditions require them.
      source: twospi-sds
      where: Section 8.2.2 (Individual protection measures)
uses:
  - application: thermal-control
    device: Thin SiOx film on aluminised Kapton (flight-exposed coating)
    example: One of four coatings flown on LDEF for 10 months in low Earth orbit, to test atomic-oxygen resistance and radiative properties. The 1000 Å SiOx sample eroded uniformly.
    source: nasa-ldef-1995
    where: Summary; Section 4, sample 3 (1000 Å SiOx on VDA Kapton)
  - application: batteries
    device: Silicon monoxide anode for lithium-ion cells (commercial and research)
    example: The review describes SiO as a high-capacity anode, with a delithiation potential below 0.5 V and reversible capacities of 1300 to 1700 mAh/g for commercial SiO materials, and calls its volume change and first-cycle losses the main barriers to commercial use.
    source: zhu2022
    where: English abstract, first paragraph
  - application: optics-and-cameras
    device: Thermally evaporated SiO films for optical coatings
    example: A CSIC optics group measured the transmittance of thermally evaporated SiO films from 7.1 to 800 eV, and derived their optical constants with a Kramers-Kronig analysis. The Wikipedia article states that commercially available solid SiO is used to deposit SiO films.
    source: csic-sio-optics
    where: Abstract
supply:
  - subject: Silicon metal (feedstock for SiO)
    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
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (silicon added in the 2025 list)
        listed: true
      - list: EU critical raw materials list (2023 list of 34, shown on the Commission page as Silicon metal)
        listed: true
    recycling: 'USGS silicon chapter: ''Recycling: Insignificant.'''
    substitutes:
      - 'USGS: gallium arsenide and germanium are the principal substitutes for silicon in semiconductor and infrared applications; the chapter names no substitute for SiO.'
    source: usgs-mcs2026-silicon
    where: World Production table, silicon metal 2025 (world total 4,600 thousand t silicon content; shares calculated by Space Mushroom from the country values); Events, Trends and Issues (China almost 80% of global silicon materials in 2025, ferrosilicon included); Recycling; Substitutes; 2025 critical list text. The EU list is on the Commission page, critical raw materials list, 2023.
documents:
  - title: 'PubChem: Silicon oxide (SiO), CID 66241, GHS classification and experimental properties'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/66241
    year: 2026
  - title: 'SPI Supplies safety data sheet: SPI-Chem Silicon Monoxide (SiO) Chips, 3 to 6 mm'
    type: sds
    url: https://www.2spi.com/catalog/documents/01813-SiliconMonoxideChips-20180123.pdf
    year: 2018
  - title: 'Angstrom Sciences safety data sheet: Silicon Monoxide'
    type: sds
    url: https://angstromsciences.com/wp-content/uploads/files/SDS/Silicon%20Monoxide.pdf
    year: 2015
  - title: 'Stanford Advanced Materials material safety data sheet: Silicon Monoxide'
    type: sds
    url: https://www.sputtertargets.net/Public/pdf/silicon-monoxide-msds.pdf
    year: 2012
  - title: 'USGS Mineral Commodity Summaries 2026: Silicon'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf
    year: 2026
  - title: 'NASA: Four Space Long-Duration Exposure Facility (LDEF) Material Coatings (NTRS N95-23913)'
    type: report
    url: https://ntrs.nasa.gov/api/citations/19950017493/downloads/19950017493.pdf
    year: 1995
  - title: Research Progresses on Structural Optimization and Interfacial Modification of Silicon Monoxide Anode for Lithium-Ion Battery (Acta Physico-Chimica Sinica, 2022)
    type: paper
    url: https://jbzhao.xmu.edu.cn/191.pdf
    year: 2022
  - title: Optical constants of evaporation-deposited silicon monoxide films in the 7.1-800 eV photon energy range (CSIC)
    type: paper
    url: https://gold.io.csic.es/optical-constants-of-evaporation-deposited-silicon-monoxide-films-in-the-7-1-800-ev-photon-energy-range/
    year: 2009
gaps:
  - No vacuum outgassing (TML or CVCM) result for silicon monoxide was found in a source opened for this profile. The flight result is for a SiOx coating on Kapton, not for bulk SiO.
  - Refractive index of evaporated SiO was not found as a number. The CSIC abstract gives no value. A thesis on reactive evaporation gives 1.57 to 3.93 for silicon oxides in general, which is not SiO-specific, so it is not used.
  - The electrical conductivity of 6.7 × 10^-4 S/cm (review, English abstract) is printed with an exponent, which this file does not use. It is left out until it can be checked by hand against the printed value.
  - PubChem prints an experimental density of 2.15 at 25 °C with no unit. It is left out because the unit was not printed.
  - Atomic weights for silicon and oxygen were not read in a source opened for this profile, so the recipe parts carry no atoms or atomic_weight.
  - Crustal abundance of silicon was not found in a source opened for this profile.
  - Disproportionation of solid SiO into silicon and silicon dioxide on heating (400 to 800 °C) appears in the Wikipedia article only. It is not used as a property or ageing entry until a primary source is read.
  - The EMD Group product sheet (SiO optical data and evaporation conditions), the American Elements SDS, and the RSC Materials Advances SiOx review returned HTTP 403 and were not read. Their values are not used.
  - Evaporation process values (boat material, evaporation temperature, oxygen partial pressure) were not read from a page that could be opened.
  - Pure-SiO first-cycle Coulombic efficiency and cycle life were not read as numbers in an open source. The review figures are for composites or modified materials.
  - 'Non-canon property names used: electrical_conductivity is not used here, delithiation_potential and specific_capacity are short snake_case names, because no canon name fits.'
  - 'Hazard data conflict: PubChem and the Stanford SDS list irritation, while the SPI SDS lists no hazard classification. Both are kept with their sources.'
  - The Xiamen review's licence and open-access status were not checked, so it is cited as a paper with licence not checked.
sources:
  pubchem-sio:
    title: PubChem compound record, Silicon oxide (SiO), CID 66241
    id: CID 66241; CAS 10097-28-6
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/66241/JSON
    year: 2026
    kind: database
    license: public domain (NCBI)
  wikipedia-sio:
    title: 'Wikipedia: Silicon monoxide (composition, production and history only)'
    id: Wikipedia article, read 2026-10-26
    url: https://en.wikipedia.org/wiki/Silicon_monoxide
    year: 2026
    kind: web
    license: CC BY-SA 4.0
  twospi-sds:
    title: 'SPI Supplies safety data sheet: SPI-Chem Silicon Monoxide (SiO) Chips, 3 to 6 mm'
    id: SPI catalog 01813-BA, 01813-CF, 01813-MB; effective 23 January 2018
    url: https://www.2spi.com/catalog/documents/01813-SiliconMonoxideChips-20180123.pdf
    year: 2018
    kind: datasheet
    license: supplier document, linked not reproduced
  angstrom-sds:
    title: 'Angstrom Sciences safety data sheet: Silicon Monoxide'
    id: Revision 07/14/15; CAS 10097-28-6; EC 233-232-8
    url: https://angstromsciences.com/wp-content/uploads/files/SDS/Silicon%20Monoxide.pdf
    year: 2015
    kind: datasheet
    license: supplier document, linked not reproduced
  sam-sds:
    title: 'Stanford Advanced Materials material safety data sheet: Silicon Monoxide'
    id: Version 2.0, revision date 5 September 2012
    url: https://www.sputtertargets.net/Public/pdf/silicon-monoxide-msds.pdf
    year: 2012
    kind: datasheet
    license: supplier document, linked not reproduced
  usgs-mcs2026-silicon:
    title: 'Mineral Commodity Summaries 2026: Silicon'
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  ec-crm:
    title: 'Critical raw materials (European Commission): 2023 list of 34 critical raw materials'
    id: EU critical raw materials list, 2023 (fifth list)
    url: https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en
    year: 2023
    kind: web
    license: European Commission web page
  zhu2022:
    title: Research Progresses on Structural Optimization and Interfacial Modification of Silicon Monoxide Anode for Lithium-Ion Battery
    id: doi:10.3866/PKU.WHXB202103052 (Acta Physico-Chimica Sinica 38, 2103052)
    url: https://jbzhao.xmu.edu.cn/191.pdf
    year: 2022
    kind: paper
    license: not checked
  nasa-ldef-1995:
    title: Four Space Long-Duration Exposure Facility (LDEF) Material Coatings
    id: NASA Goddard Space Flight Center; NTRS N95-23913 (ID 19950017493)
    url: https://ntrs.nasa.gov/api/citations/19950017493/downloads/19950017493.pdf
    year: 1995
    kind: report
    license: public domain (NASA)
  csic-sio-optics:
    title: Optical constants of evaporation-deposited silicon monoxide films in the 7.1-800 eV photon energy range
    id: Fernandez-Perea et al. (Instituto de Optica, CSIC), 2009
    url: https://gold.io.csic.es/optical-constants-of-evaporation-deposited-silicon-monoxide-films-in-the-7-1-800-ev-photon-energy-range/
    year: 2009
    kind: paper
    license: not checked
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 14
  unreachable: 4
  caveats: 4
  note: 'Read by an AI assistant on 2026-10-26 from the PDFs and pages fetched in that run. The EMD Group, American Elements, RSC and uca.es pages returned HTTP 403 and are not used. The composition, production and history statements come from Wikipedia only. Caveats: the LDEF values are for a SiOx coating on Kapton, not bulk SiO; the anode figures are from a review abstract and are not measured here; the two SDS sources disagree on hazard classification; the 2043 mAh/g figure is not stated as theoretical.'
story:
  recipe:
    line: SiO is silicon monoxide. Silicon carries the +2 oxidation state, and each silicon is bonded to one oxygen. Solid SiO is a brown-black, glassy polymer, (SiO)n, and it is made by heating silica with silicon or by reducing silica at high temperature.
    parts:
      - name: Silicon
        symbol: Si
        role: The main element. In SiO it is in the +2 oxidation state (Wikipedia).
      - name: Oxygen
        symbol: O
        role: One oxygen per silicon. In an anode, lithium silicate and lithium oxide form from the SiO in the first cycle (review).
  risk_groups:
    - title: For people
      level: 1
      verdict: Irritant dust; one SDS lists no hazard
      lead: Supplier data disagree. PubChem and one SDS report skin, eye and respiratory irritation, while the 2018 SPI SDS reports no hazard classification.
      points:
        - label: The powder
          line: PubChem's aggregated record reports skin irritation (H315), serious eye irritation (H319) and a single-exposure respiratory irritation (H335) in most of its 327 company reports. The SPI SDS classifies it as not hazardous.
        - label: Dust limits
          line: The SPI SDS gives a TLV of 10 mg/m3 and an OSHA PEL of 15 mg/m3 for total dust.
        - label: Long-term lung effects
          line: The Stanford SDS says chronic inhalation may cause pneumoconiosis, pulmonary fibrosis and silicosis. It cites no test for SiO itself.
    - title: If it fails
      lead: These results come from anode tests and one space coating, not from incidents in service.
      points:
        - label: Anode swelling
          line: A SiO anode changes volume by about 200% on cycling, which can pulverise it and make it detach from the current collector.
        - label: First cycle
          line: Lithium silicate and lithium oxide form irreversibly in the first cycle, which lowers the initial efficiency.
        - label: Space erosion
          line: A 1000 Å SiOx coating on Kapton eroded uniformly on LDEF, with minor changes in its solar absorptance, over 10 months in low Earth orbit.
    - title: Handling and storage
      points:
        - label: Storage
          line: Keep the material tightly closed in a cool, dry place, away from strong oxidising agents, strong acids and strong bases.
        - label: Dust
          line: Use local exhaust where dust forms, and a NIOSH approved dust respirator or an N95 or P1 mask where nuisance dust is a concern.
  why: Silicon monoxide (SiO) is a black, water-insoluble solid. Its evaporated films serve optical coatings, and its powder is a high-capacity lithium-ion anode material. The two uses need different things. Optical films need a stable, reproducible deposit, while a battery anode must survive a volume change of about 200% on cycling. The space record covers only a SiOx coating on Kapton, which eroded uniformly and changed little in its absorptance during 10 months in low Earth orbit.
  uses:
    - where: Optical coatings
      line: A CSIC optics group measured the optical constants of thermally evaporated SiO films from 7.1 to 800 eV. Commercial solid SiO is used to deposit SiO films, according to the Wikipedia article.
    - where: Lithium-ion anodes
      line: The Xiamen review describes SiO as a high-capacity anode, with a delithiation potential below 0.5 V and reversible capacities of 1300 to 1700 mAh/g for commercial SiO. Its volume change and first-cycle losses remain the main barriers.
    - where: Thermal-control film in space
      line: A 1000 Å SiOx coating on aluminised Kapton flew on LDEF for 10 months in low Earth orbit. It eroded uniformly, and its integrated solar absorptance went from 0.363 (unflown control) to 0.391 (flown).
  can_do:
    - label: Solar absorptance
      value: 0.363 to 0.391
      line: The 1000 Å SiOx coating had an integrated solar absorptance of 0.363 as an unflown control and 0.391 after the flight. Its emittance was 0.564 for the control and 0.547 for the flown sample.
    - label: Capacity
      value: 1300 to 1700 mAh/g
      line: The review reports a reversible capacity of 1300 to 1700 mAh/g for commercial SiO, and quotes a high specific capacity of about 2043 mAh/g.
    - label: Melting point
      value: 1702 °C
      line: The supplier SDS sheets print a melting point of 1702 °C (1702.0 °C and 1702.00 °C), and the Angstrom Sciences SDS gives it as greater than 1702 °C.
    - label: Density
      value: 2.13 g/cc
      line: The Angstrom Sciences SDS prints a density of 2.13 g/cc, and the SPI SDS prints a specific gravity of 2.13 relative to water.
  compare: SiO trades stability for capacity. The review quotes a high specific capacity of about 2043 mAh/g, well above the practical capacity of commercial graphite anodes, but a volume change of about 200% and a low first-cycle efficiency keep it from simple use. As a thin film, its value is evaporation behaviour and flight stability rather than bulk strength. The table compares SiO's melting point, density and capacity.
  compare_rows:
    - label: Melting point
      benchmark: melting_point
    - label: Density
      benchmark: density
    - label: Capacity in a lithium-ion anode
      benchmark: practical_capacity
  handling:
    - Store the material tightly closed, cool and dry, away from strong oxidisers, acids and bases.
    - Use local exhaust where dust forms, and a dust respirator where nuisance dust is a concern.
    - Treat the hazard classification as unsettled, since PubChem and the SPI SDS disagree.
  good_for:
    - Optical films. A CSIC group measured the optical constants of thermally evaporated SiO films from 7.1 to 800 eV.
    - High capacity in an anode. The review quotes 1300 to 1700 mAh/g for commercial SiO.
    - Thin low-absorptance films in orbit. A 1000 Å SiOx coating changed from 0.363 to 0.391 solar absorptance over 10 months on LDEF.
  watch_out:
    - Volume change of about 200% on cycling, which pulverises an anode.
    - Low first-cycle Coulombic efficiency from irreversible lithium silicate and lithium oxide.
    - The space test is a SiOx coating on Kapton, not bulk SiO.
    - The two SDS sheets disagree on hazard classification, so check the supplier SDS for the lot you hold.
  verdict: SiO is a useful evaporation material for thin films and a high-capacity but unstable anode. The space record is a SiOx coating on Kapton that changed little in 10 months in orbit, so it supports thin-film thermal-control use, not bulk parts.