spore: profile
id: silver
spore_version: 0.2
family: precious-metals
name: Silver
abbreviation: Ag
role: conductor / reflector / thermal-control layer
category: metals
type: precious-metals
summary: |
  Silver is a soft, dense, face-centred cubic metal with the highest electrical conductivity of any metal. A Goodfellow datasheet gives an electrical resistivity of 1.63 microohm cm and a thermal conductivity of 429 W/(m K). On spacecraft it is the reflecting layer in silvered Teflon thermal blankets and the last contact metal on some solar cells. Bare silver tarnishes in sulphur-bearing air and is attacked by atomic oxygen in low Earth orbit, so in orbit it is nearly always covered.
best_for: Electrical and heat conduction and light reflection (resistivity 1.63 microohm cm, thermal conductivity 429 W/(m K) at 0 to 100 degC)
weakest_at: Unprotected exposure to atomic oxygen in low Earth orbit (black oxide that cracks and spalls) and to sulphur compounds in air (silver sulphide tarnish)
identity:
  formula: Ag
  cas: 7440-22-4
  crystal_system: face-centred cubic
  source: goodfellow-ag
  where: Atomic Properties table (crystal structure, atomic number 47, atomic weight 107.8682); CAS 7440-22-4 from the PubChem Silver record (CID 23954), CAS section
tags:
  environments:
    - low-earth-orbit
  stresses:
    - atomic-oxygen
    - thermal-cycling
    - micrometeoroids-and-debris
  applications:
    - thermal-control
    - solar-arrays
    - electronics-and-chips
    - optics-and-cameras
properties:
  - benchmark: density
    label: Density at 20 degC
    value: 10.5
    unit: g/cm3
    scope: material
    conditions:
      material: bar, purity 99.95%
      temperature: 20 degC
    method: Value listed in the supplier's online property table (Goodfellow SKU 1000002903)
    status: ground
    note: Other density entries exist for silver; see the Merck Index value below.
    source: goodfellow-ag
    where: Physical Properties table
  - benchmark: density_merck_15c
    label: Density at 15 degC (Merck Index, as quoted by PubChem)
    value: 10.49
    unit: g/cm3
    scope: material
    conditions:
      temperature: 15 degC
      citation: Merck Index, 13th ed., 2001, p. 1525, as listed in the PubChem record
    method: Reference-book value quoted in the PubChem Density section
    status: ground
    note: The same PubChem section also lists 10.5 at 68 degF (NTP, OSHA) and 10.49 for the metal (NIOSH).
    source: pubchem-silver
    where: Density section, record CID 23954
  - benchmark: melting_point
    label: Melting point
    value: 961.9
    unit: degC
    scope: material
    conditions:
      material: bar, purity 99.95%
    method: Value listed in the supplier's online property table
    status: ground
    source: goodfellow-ag
    where: Thermal Properties table
  - benchmark: boiling_point
    label: Boiling point
    value: 2212
    unit: degC
    scope: material
    conditions:
      material: bar, purity 99.95%
    method: Value listed in the supplier's online property table
    status: ground
    source: goodfellow-ag
    where: Physical Properties table
  - benchmark: electrical_resistivity
    label: Electrical resistivity at 20 degC
    value: 1.63
    unit: microohm cm
    scope: material
    conditions:
      material: bar, purity 99.95%
      temperature: 20 degC
    method: Value listed in the supplier's online property table
    status: ground
    note: The same table gives a temperature coefficient of 0.0041 per K over 0 to 100 degC. The Wikipedia infobox lists 15.87 nOhm m (about 1.587 microohm cm) at 20 degC, a slightly lower figure for a purer specimen or a different source, so resistivity varies between references.
    source: goodfellow-ag
    where: Electrical Properties table
  - benchmark: thermal_conductivity
    label: Thermal conductivity
    value: 429
    unit: W/(m K)
    scope: material
    conditions:
      material: bar, purity 99.95%
      temperature: 0 to 100 degC
    method: Value listed in the supplier's online property table
    status: ground
    note: The Wikipedia infobox also lists 429 W/(m K).
    source: goodfellow-ag
    where: Thermal Properties table
  - benchmark: cte
    label: Coefficient of thermal expansion
    value: 19.1
    unit: ppm/K
    scope: material
    conditions:
      material: bar, purity 99.95%
      temperature: 0 to 100 degC
    method: Value listed in the supplier's online property table (written there as x10^-6 per K)
    status: ground
    source: goodfellow-ag
    where: Thermal Properties table
  - benchmark: specific_heat
    label: Specific heat
    value: 237
    unit: J/(K kg)
    scope: material
    conditions:
      material: bar, purity 99.95%
      temperature: 25 degC
    method: Value listed in the supplier's online property table
    status: ground
    source: goodfellow-ag
    where: Thermal Properties table
  - benchmark: latent_heat_of_fusion
    label: Latent heat of fusion
    value: 103
    unit: J/g
    scope: material
    conditions:
      material: bar, purity 99.95%
    method: Value listed in the supplier's online property table
    status: ground
    note: The same table gives a latent heat of evaporation of 2390 J/g.
    source: goodfellow-ag
    where: Thermal Properties table
  - benchmark: tensile_modulus
    label: Tensile modulus
    value: 82.7
    unit: GPa
    scope: material
    conditions:
      material: bar, purity 99.95%
      condition: listed for both hard and soft
    method: Value listed in the supplier's online property table
    status: ground
    source: goodfellow-ag
    where: Mechanical Properties table
  - benchmark: tensile_strength_hard
    label: Tensile strength, hard condition
    value: 330
    unit: MPa
    scope: material
    conditions:
      material: bar, purity 99.95%
      condition: hard
    method: Value listed in the supplier's online property table (condition read from the table's Hard and Soft columns)
    status: ground
    note: The supplier does not state the test standard or temperature.
    source: goodfellow-ag
    where: Mechanical Properties table
  - benchmark: tensile_strength_soft
    label: Tensile strength, soft condition
    value: 172
    unit: MPa
    scope: material
    conditions:
      material: bar, purity 99.95%
      condition: soft
    method: Value listed in the supplier's online property table (condition read from the table's Hard and Soft columns)
    status: ground
    note: The supplier does not state the test standard or temperature.
    source: goodfellow-ag
    where: Mechanical Properties table
  - benchmark: hardness_vickers_hard
    label: Vickers hardness, hard condition
    value: 95
    unit: kgf/mm2
    scope: material
    conditions:
      material: bar, purity 99.95%
      condition: hard
    method: Value listed in the supplier's online property table
    status: ground
    source: goodfellow-ag
    where: Mechanical Properties table
  - benchmark: hardness_vickers_soft
    label: Vickers hardness, soft condition
    value: 25
    unit: kgf/mm2
    scope: material
    conditions:
      material: bar, purity 99.95%
      condition: soft
    method: Value listed in the supplier's online property table
    status: ground
    source: goodfellow-ag
    where: Mechanical Properties table
  - benchmark: poissons_ratio
    label: Poisson's ratio
    value: 0.367
    unit: dimensionless
    scope: material
    conditions:
      material: bar, purity 99.95%
      condition: listed for both hard and soft
    method: Value listed in the supplier's online property table
    status: ground
    note: The same table lists a bulk modulus of 103.6 GPa.
    source: goodfellow-ag
    where: Mechanical Properties table
  - benchmark: reflectance_500nm_200nm_ag
    label: Designed reflectivity at 500 nm of a 200 nm silver layer in a telescope coating
    value: 97.85
    unit: '%'
    scope: material
    conditions:
      wavelength: 500 nm
      silver_thickness: 200 nm
      coating: silver with protective and enhancing layers, not bare silver
    method: Designed (optical-model) value listed in the paper's Table 2
    status: prediction
    note: The paper's abstract reports an average measured specular reflectivity of about 98% from 400 to 1000 nm for the finished enhanced coating. The 86 nm and 130 nm layers gave 97.43% and 97.83% at 500 nm. This is a protected coating design, not bare silver.
    source: wu2022
    where: Table 2; abstract
  - benchmark: ssm_silver_layer_thickness
    label: Silver layer in silvered FEP Teflon thermal blanket material
    value: 1600
    unit: angstrom
    scope: material
    conditions:
      construction: 5 mil FEP Type A Teflon film, vapour-deposited silver on the back, then about 400 angstrom of Inconel, then 3 to 5 mil black urethane-base paint when used as a blanket
    method: Construction described in the NASA report (stated as 'approximately 1600A')
    status: flight
    note: The specimens flew on LDEF for 5 years and 9 months.
    source: young1991
    where: Section 1 (Introduction) and Figure 2
  - benchmark: ao_oxidation_activation_energy
    label: Empirical activation energy of silver oxidation by atomic oxygen (early growth)
    value: 0.1
    unit: eV
    scope: material
    conditions:
      temperature_range: 0 to 70 degC in 10 degC steps
      sample: evaporated silver about 10000 angstrom thick on silicon
      oxygen_source: plasma asher at 60 W and 800 millitorr, flux estimated at 1e18 per cm2 s
    method: Ellipsometer thickness measurements between exposures, Arrhenius plots; the abstract says 'of the order of 0.1 eV'
    status: ground
    note: The oxide film thickness grew as the logarithm of exposure time in the early phase. This is a ground plasma test, not a flight rate.
    source: fromhold1988
    where: Abstract
  - benchmark: pcb_silver_content
    label: Silver in whole mobile-phone circuit boards, aqua regia leach
    value: 123.35
    unit: g/ton of PCB
    scope: material
    conditions:
      sample: whole circuit boards from mobile phones of one brand and model, about 30 g
      leach: aqua regia, solid to liquid 1 to 20, 2 hours at 60 degC
      analysis: flame atomic absorption
    method: Single characterisation test, reported in the paper's Table 3
    status: ground
    uncertainty: The paper prints 123.35 in Table 3, 123.85 in the abstract and 123.25 in the conclusions. No repeats are reported.
    note: One brand and model only, so it is not an industry average. The Introduction quotes a literature figure of 250 mg silver in the metal fraction and, for mobile phones, 3.5 kg of silver per ton of material (second-hand, from other authors).
    source: petter2015
    where: Table 3; Section 2 (Materials and methods)
  - benchmark: pv_silver_use_per_watt
    label: Total silver use in a record-low silicon heterojunction solar cell
    value: 1.4
    unit: mg/Wp
    scope: cell
    conditions:
      cell: silicon heterojunction
      front: silver-copper paste
      rear: pure copper paste
    method: Result reported in a Fraunhofer ISE press release
    status: ground
    note: The press release says this is about one tenth of the current standard in industrial production and gives 2 mg/Wp as the calculated long-term sustainable target. It does not give the industrial figure.
    source: fraunhofer2025
    where: Press release of 28 April 2025
corrosion:
  - environment: Atomic oxygen in low Earth orbit
    headline: Exposed silver is quickly turned into a black oxide that cracks and flakes off.
    effect: An Auburn University study for NASA states that silver is swiftly attacked by atomic oxygen to form a black oxide layer that subsequently cracks and spalls. On the Solar Maximum Mission, Inconel-protected silver coatings on Teflon showed near total silver reaction and flaking, blackening the strips of tape with a direct view of the orbital environment. On LDEF, silver beneath a micrometeoroid hole in the FEP cover was oxidised to silver oxide in rings around the hole.
    rating: severe
    conditions:
      smm: Solar Maximum Mission, about 4 years in orbit, Inconel/silver on FEP Teflon
      ldef: 5 years 9 months, 477 km mean altitude (de Rooij gives 335 km at retrieval)
      lab: plasma asher, 0 to 70 degC
    source: fromhold1988
    where: Section I (Introduction); Linton and Whitaker abstract; de Rooij Results and discussion
  - environment: Sulphur compounds in air (tarnish)
    headline: Hydrogen sulphide in air turns silver into dark silver sulphide, which absorbs visible light.
    effect: A 2022 telescope-coating paper says H2S in air reacts with the silver to form Ag2S, which absorbs visible light and is the main cause of the black tarnish on bare silver. Silver oxides (AgOx) can form by a separate route involving water. In its accelerated sulphur test, a 130 nm silver layer fell to about 82% reflectivity near 500 nm and an 86 nm layer to very low reflectivity near 480 nm, while a 200 nm layer kept an average above 97%.
    rating: moderate
    conditions:
      test: ZnS heated in vacuum chamber at 5e-3 Pa, 10 min exposure at room temperature
      comparison: the paper cites ANSI/EIA-977 as 480 h at 60 degC or 750 h at 105 degC
    source: wu2022
    where: Introduction; Sections 3.2 and 4; Section 2.3
  - environment: Atomic-oxygen roughening of silvered FEP Teflon
    headline: The Teflon cover is eroded and the blanket goes from mirror-like to frosted, but silver under it is protected until the cover is breached.
    effect: Silvered FEP specimens from LDEF changed from specular to diffuse reflectors in step with atomic-oxygen fluence, because atomic oxygen roughened the coating surface. XPS, infrared and thermal analysis found no significant change at the molecular level.
    rating: low
    conditions:
      exposure: 5 years and 9 months on LDEF
      positions: Row 3 trailing edge stayed specular; Row 9 leading edge turned frosted
    source: young1991
    where: Abstract; Section 3
risks:
  hazards:
    - text: 'PubChem (CID 23954) lists several classifications. EU CLP for silver massive (1 mm or larger): warning, suspected of damaging fertility (H361f) and may cause organ damage through prolonged or repeated exposure (H373). For silver powder and nano silver it adds very toxic to aquatic life (H400) and with long-lasting effects (H410). The ECHA aggregate of 2,154 notifications shows H400 and H410 as the main codes, and 28.9% of reports say the substance does not meet GHS hazard criteria. The classification therefore depends on the notifier and the form.'
      ghs:
        - H361f
        - H373
        - H400
        - H410
      source: pubchem-silver
      where: GHS Classification section
  failure_risks:
    - mode: Silver oxide blackening and flaking in orbit
      trigger: Direct exposure of bare or thinly covered silver to atomic oxygen, as on Solar Maximum Mission thermal tape
      consequence: Near total silver reaction and flaking, with erosion of the Teflon underneath; the reflecting layer is lost.
      severity: high
      source: linton1987
      where: Abstract
    - mode: Oxidation of the silver at micrometeoroid holes
      trigger: A micrometeoroid hole through the FEP cover on LDEF
      consequence: Atomic oxygen reached the silver through the hole and formed rings of silver oxide; the silver layer had locally debonded from the FEP.
      severity: moderate
      source: derooij1992
      where: Results and discussion
    - mode: Sulphide tarnish before launch
      trigger: Hydrogen sulphide in air
      consequence: Ag2S forms, absorbs visible light and darkens the surface (observed in a ground test with thin layers losing reflectivity).
      severity: moderate
      source: wu2022
      where: Section 4
  side_effects:
    - text: Silver oxide has a much higher electrical resistance than silver, so oxidation can be followed by the resistance of a thin film. A NASA-related technique uses 250 angstrom silver films as atomic-oxygen sensors under candidate coatings.
      affects: Coating tests for atomic-oxygen resistance
      source: lan1989
      where: Technique to evaluate coatings; Q-atom beam flux calibration
    - text: Silicon-containing molecular contamination on silvered FEP from LDEF was discussed as a possible influence on the atomic-oxygen response.
      affects: Interpretation of the LDEF result
      source: young1991
      where: Abstract
  handling:
    - text: The PubChem record shows hazard classification varies by form; check the safety data sheet for the specific form (bulk, powder or nano) before handling.
      source: pubchem-silver
      where: GHS Classification section
  mitigations:
    - text: On spacecraft thermal blankets the silver is placed behind a transparent FEP Teflon film and covered with Inconel, so the silver faces the film and not the space environment.
      source: young1991
      where: Section 1 and Figure 2
    - text: For mirrors, a thicker silver layer (200 nm kept an average reflectivity above 97% after the sulphur test) and protective layers are used; the 130 nm layer averaged about 90%.
      source: wu2022
      where: Sections 3.2 and 4
uses:
  - application: thermal-control
    device: Silvered FEP Teflon (second-surface mirror) thermal blankets
    example: Silvered FEP blankets flew on LDEF for 5 years and 9 months, and Inconel-silver coated FEP Teflon was recovered from the Solar Maximum Mission.
    source: young1991
    where: Section 1; Linton and Whitaker abstract
  - application: solar-arrays
    device: Final contact metal on GaAs solar cells and evaporated contacts on thin silicon cells, with silver-plated Invar interconnect tabs
    example: A TRW and JPL study assembled 300 GaAs and 300 fifty-micron silicon cells, interconnected with silver plated Invar tabs by welding.
    source: trw1984
    where: Summary; Section on cell description
  - application: solar-arrays
    device: Screen-printed silver ink front contacts for photovoltaic cells (research)
    example: A Purdue and JPL study of metallo-organic decomposition silver inks for solar-cell metallization, covering screen printing, firing, sheet resistance and solderability.
    source: purdue1985
    where: Title, contents list
  - application: electronics-and-chips
    device: Mobile-phone printed circuit boards
    example: Holgersson et al. measured silver, gold and palladium in the boards of 30 mobile phones and 30 smartphones; Petter et al. found 123.35 g of silver per ton in one phone-board sample.
    source: holgersson2018
    where: Abstract (Chalmers record); Petter Table 3
  - application: electronics-and-chips
    device: Electrical and electronics, brazing and solder
    example: USGS estimates 2025 US silver uses of electrical and electronics 25%, photovoltaics 15%, and brazing and solder 3%.
    source: usgs-mcs2026
    where: Domestic Production and Use
  - application: optics-and-cameras
    device: Telescope mirror coating
    example: A silver-enhanced coating with an average specular reflectivity of about 98% from 400 to 1000 nm, tested for sulphur resistance.
    source: wu2022
    where: Abstract
supply:
  - subject: Silver
    abundance: 'USGS: silver is primarily obtained as a byproduct from lead-zinc, copper and gold mines; polymetallic deposits account for more than two-thirds of US and world resources. World mine production 25,300 tons in 2024 and an estimated 26,000 tons in 2025. World reserves 610,000 tons.'
    producers:
      - country: Mexico
        share_percent: 24.2
        year: 2025
      - country: Peru
        share_percent: 13.8
        year: 2025
      - country: China
        share_percent: 13.1
        year: 2025
      - country: Bolivia
        share_percent: 5.8
        year: 2025
      - country: Chile
        share_percent: 5.4
        year: 2025
    critical_lists:
      - list: US Final 2025 List of Critical Minerals (silver added; 90 FR 50494, 7 November 2025)
        listed: true
    recycling: 'USGS: in 2025 about 1,000 tons of silver was recovered from new and old scrap, about 11% of US apparent consumption. US net import reliance 77% in 2025.'
    substitutes:
      - 'USGS: aluminium and rhodium may replace silver in mirrors and other reflecting surfaces; digital imaging replaces photographic silver; stainless steel and other metals replace silver in some surgical and tableware uses; nonsilver batteries may replace silver batteries in some applications.'
    source: usgs-mcs2026
    where: Mineral Commodity Summaries 2026, Silver chapter; shares are calculated by Space Mushroom from the 2025 estimated mine production table (6,300, 3,600, 3,400, 1,500 and 1,400 tons of 26,000 tons)
documents:
  - {title: "WebElements: Silver, the essentials", type: database, url: "https://winter.group.shef.ac.uk/webelements/silver/", year: 2026}
  - {title: "WebElements: Silver, crystal structure", type: database, url: "https://winter.group.shef.ac.uk/webelements/silver/crystal_structure.html", year: 2026}
  - title: Goodfellow silver bar properties page (SKU 1000002903)
    type: datasheet
    url: https://www.goodfellow.com/uk/silver-bar-1000002903
    year: 2025
  - title: 'PubChem compound record: Silver (CID 23954)'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/Silver
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Silver'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silver.pdf
    year: 2026
  - title: Experimental results on atomic oxygen corrosion of silver (Fromhold, NASA/ASEE 1988)
    type: report
    url: https://ntrs.nasa.gov/api/citations/19890012367/downloads/19890012367.pdf
    year: 1988
  - title: 'NASA TM-104096: An analysis of LDEF-exposed silvered FEP Teflon thermal blanket material'
    type: report
    url: https://ntrs.nasa.gov/api/citations/19920005971/downloads/19920005971.pdf
    year: 1991
gaps:
  - No opened primary source for the reflectivity of bare (unprotected) silver across the spectrum; the only reflectivity value entered is for a protected telescope-coating design (Wu et al. Table 2), and it is a model value.
  - No numeric atomic-oxygen erosion yield or mass-loss rate for bare silver in cm3/atom was found. Fromhold gives an activation energy and growth law only, and the SMM and LDEF reports are descriptive.
  - Fromhold's oxide thickness against time at each temperature (the figures and tables) was not read, so no oxide growth numbers are entered.
  - The tarnish rate of silver in real air (sulphur dose, years to visible tarnish) was not sourced; only an accelerated ZnS vacuum test is entered.
  - Holgersson et al. (Resources, Conservation and Recycling 2018) measured silver in 30 mobile phones and 30 smartphones, but the paper is not open access and only its abstract page was read, so no silver concentrations from it are entered.
  - The Goodfellow tensile strength and hardness values do not state a test standard, temperature or purity condition beyond the bar listing.
  - No open source was found for silver solder or silver-filled conductive paste properties for spacecraft (alloy composition, melting range, paste resistivity); the USGS 3% brazing and solder share is the only solder figure.
  - No source was opened for silver on spacecraft solar-cell grids beyond the TRW and JPL 1984 report (silver as final contact metal) and the Purdue 1985 MOD silver ink study (only the title and table of contents were read).
  - No outgassing, vacuum cold-welding, radiation tolerance or cryogenic data for silver were looked for.
  - The statement that silver has the highest electrical and thermal conductivity of any metal rests on Wikipedia (which cites Hammond); no primary handbook page was opened. The Wikipedia text says thermal conductivity is 'among the highest of all materials'.
  - The Ag Mohs/ductility, magnetic and optical-constant data were not collected.
sources:
  webelements-silver-main:
    title: "Silver - 47Ag: the essentials (WebElements, relative atomic mass)"
    url: https://winter.group.shef.ac.uk/webelements/silver/
    year: 2026
    kind: database
    license: "WebElements, free online reference"
  webelements-silver-crystal:
    title: "Silver - 47Ag: crystal structure (WebElements)"
    url: https://winter.group.shef.ac.uk/webelements/silver/crystal_structure.html
    year: 2026
    kind: database
    license: "WebElements, free online reference"
  goodfellow-ag:
    title: Silver Bar - properties table (Goodfellow, purity 99.95%)
    id: Goodfellow SKU 1000002903, accessed 2026-10-17
    url: https://www.goodfellow.com/uk/silver-bar-1000002903
    year: 2025
    kind: datasheet
    license: supplier web page, cited not reproduced
  pubchem-silver:
    title: 'PubChem compound record: Silver (CID 23954)'
    id: CID 23954; CAS 7440-22-4
    url: https://pubchem.ncbi.nlm.nih.gov/compound/Silver
    year: 2026
    kind: database
    license: public domain (NCBI)
  usgs-mcs2026:
    title: 'Mineral Commodity Summaries 2026: Silver'
    id: U.S. Geological Survey, February 2026 (prepared by Anne M. Hartingh)
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silver.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  fromhold1988:
    title: Experimental Results on Atomic Oxygen Corrosion of Silver (NASA/ASEE Summer Faculty Fellowship Program, Marshall Space Flight Center)
    id: A. T. Fromhold, Auburn University, 15 August 1988, NTRS 19890012367
    url: https://ntrs.nasa.gov/api/citations/19890012367/downloads/19890012367.pdf
    year: 1988
    kind: report
    license: public domain (NASA-sponsored report)
  linton1987:
    title: SSM Atomic Oxygen Reactions on Kapton and Silverized Teflon
    id: R. Linton and A. Whitaker, NTRS 19870004955 (N87-14388)
    url: https://ntrs.nasa.gov/api/citations/19870004955/downloads/19870004955.pdf
    year: 1987
    kind: report
    license: public domain (NASA)
  derooij1992:
    title: Some Results of the Oxidation Investigation of Copper and Silver Samples Flown on LDEF
    id: A. de Rooij, ESA/ESTEC, NTRS 19930001392 (N93-10580)
    url: https://ntrs.nasa.gov/api/citations/19930001392/downloads/19930001392.pdf
    year: 1992
    kind: report
    license: public domain (NASA-hosted conference paper)
  young1991:
    title: An Analysis of LDEF-Exposed Silvered FEP Teflon Thermal Blanket Material
    id: NASA TM-104096, P. R. Young and W. S. Slemp, December 1991, NTRS 19920005971
    url: https://ntrs.nasa.gov/api/citations/19920005971/downloads/19920005971.pdf
    year: 1991
    kind: report
    license: public domain (NASA)
  lan1989:
    title: Atomic Oxygen Effects on Candidate Coatings for Long-Term Spacecraft in Low Earth Orbit
    id: E. H. Lan, C. A. Smith and J. B. Cross, NTRS 19890003221 (N89-12592)
    url: https://ntrs.nasa.gov/api/citations/19890003221/downloads/19890003221.pdf
    year: 1989
    kind: report
    license: public domain (NASA-hosted paper)
  wu2022:
    title: Highly Reflective Silver-Enhanced Coating with High Adhesion and Sulfurization Resistance for Telescopes
    id: doi:10.3390/nano12071054 (Nanomaterials 12, 1054, PMC9000596)
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC9000596
    year: 2022
    kind: paper
    license: CC BY 4.0
  petter2015:
    title: Leaching of gold and silver from printed circuit board of mobile phones
    id: 'REM: Revista Escola de Minas 68(1), 061-068, handle 10183/117420'
    url: https://lume.ufrgs.br/handle/10183/117420
    year: 2015
    kind: paper
    license: CC BY-NC-SA 2.5 Brazil
  holgersson2018:
    title: 'Analysis of the metal content of small-size WEEE printed circuit-boards part 1: Internet routers, mobile phones and smartphones'
    id: doi:10.1016/j.resconrec.2017.02.011 (Resources, Conservation and Recycling 133, 300-308)
    url: https://research.chalmers.se/en/publication/502981
    year: 2018
    kind: paper
    license: publisher article; only the Chalmers record page was read
  trw1984:
    title: Automated Assembly of Gallium Arsenide and Fifty-Micron Thick Silicon Solar Cell Modules, Final Test Report
    id: TRW Space and Technology Group for JPL, December 1984, NTRS 19850009055
    url: https://ntrs.nasa.gov/api/citations/19850009055/downloads/19850009055.pdf
    year: 1984
    kind: report
    license: public domain (NASA/JPL contract report)
  purdue1985:
    title: MOD Silver Metallization for Photovoltaics, Final Technical Report
    id: Purdue Research Foundation for JPL, 1 July 1985, DOE/JPL-956679-85/01, NTRS 19870004421
    url: https://ntrs.nasa.gov/api/citations/19870004421/downloads/19870004421.pdf
    year: 1985
    kind: report
    license: public domain (NASA/DOE sponsored report)
  fraunhofer2025:
    title: Silicon Heterojunction Solar Cells Realized with Record Savings in Silver (press release)
    id: Fraunhofer ISE, 28 April 2025
    url: https://www.ise.fraunhofer.de/en/press-media/news/2025/silicon-heterojunction-solar-cells-realized-with-record-savings-in-silver.html
    year: 2025
    kind: web
    license: press release, cited not reproduced
  wikipedia-silver:
    title: Silver (Wikipedia)
    id: Lead section citing 11; Characteristics section citing Hammond 2004
    url: https://en.wikipedia.org/wiki/Silver
    year: 2026
    kind: web
    license: CC BY-SA 4.0
license: CC-BY-4.0
updated: '2026-10-17'
review:
  status: draft
  method: assistant
  checked_values: 20
  unreachable: 1
  caveats: 6
  note: 'Written by an AI assistant on 2026-10-17. Goodfellow values were re-read from the page''s raw HTML table; USGS, NASA and Petter values were read in text extracted from the source PDFs; PubChem and Wu et al. values were read once through a web-page summary. The Holgersson paper could not be opened beyond its record page. Caveats: Goodfellow gives no test standard; the Petter silver value is printed three ways; the reflectivity entry is a protected-coating design; the Fromhold energy is ''of the order of''; producer shares are calculated; the conductivity ranking rests on Wikipedia.'
story:
  risk_groups:
    - title: For people
      level: 1
      verdict: Classification depends on the form
      lead: Solid silver is a low hazard, but the EU classification for bulk silver includes suspected reproductive and repeated-exposure effects, and fine powder is toxic to aquatic life.
      points:
        - label: Bulk silver
          line: The EU classification quoted by PubChem for silver massive (1 mm or larger) is a warning with H361f (suspected of damaging fertility) and H373 (organ damage through prolonged or repeated exposure).
        - label: Powder and nano silver
          line: Silver powder and nano silver add H400 and H410, very toxic to aquatic life, including with long-lasting effects.
        - label: Differing notifications
          line: Of the 2,154 company reports in the ECHA aggregate, 28.9% say the substance does not meet GHS hazard criteria, so check the safety data sheet for your supplier and form.
    - title: If it fails
      lead: These results come from flight exposures of thermal blankets and from laboratory tests, not from failures of a named spacecraft system.
      points:
        - label: Atomic oxygen
          line: On the Solar Maximum Mission, exposed Inconel-protected silver showed near total silver reaction and flaking, and the strips with a direct view of the environment blackened.
        - label: Impacts
          line: On LDEF, a micrometeoroid hole in the FEP cover let atomic oxygen reach the silver, which oxidised in rings around the hole.
        - label: Tarnish
          line: In a ground sulphur test, a thin 86 nm silver layer lost most of its reflectivity near 480 nm, while a 200 nm layer kept an average above 97%.
    - title: Handling and storage
      points:
        - label: Safety data sheet
          line: PubChem shows that classification varies by form, so use the data sheet for the specific form, whether bulk, powder or nano.
        - label: Storage in air
          line: Sulphur compounds in air tarnish silver, so bare silver parts are kept protected before use.
  why: 'Silver is a soft, dense metal, atomic number 47, with a face-centred cubic crystal structure. Its single outer electron makes it an unusually good conductor: the Goodfellow table gives an electrical resistivity of 1.63 microohm cm at 20 °C and a thermal conductivity of 429 W/(m K) between 0 and 100 °C. Wikipedia, citing a handbook, states that silver has the highest electrical conductivity of all metals. It melts at 961.9 °C and has a density of 10.5 g/cm3. The same properties make it a good mirror, which is why it sits behind the Teflon film in thermal blankets. Its weakness is chemical. Sulphur compounds in air turn it into dark silver sulphide, and atomic oxygen in low Earth orbit turns exposed silver into a black oxide that cracks and flakes away, so spacecraft use almost always buries it under another layer.'
  uses:
    - where: Thermal blankets
      line: 'Silvered FEP Teflon is a second-surface mirror: sunlight passes through the transparent film and is reflected by the silver behind it, while the film radiates heat. The LDEF specimens carried about 1600 angstrom of silver on 5 mil FEP and flew for 5 years and 9 months.'
    - where: Solar cells
      line: A TRW and JPL study used GaAs cells whose last contact metal was silver, silicon cells with evaporated silver contacts, and silver plated Invar tabs welded as interconnects. A Purdue and JPL study looked at silver inks for printed cell contacts.
    - where: Circuit boards
      line: Phone circuit boards contain silver. One study leached whole boards from a single phone model and found 123.35 g of silver per ton of boards, while a Chalmers study measured silver in 30 mobile phones and 30 smartphones.
    - where: Mirrors and optics
      line: A silver telescope coating reached an average specular reflectivity of about 98% between 400 and 1000 nm.
  can_do:
    - label: Conduct electricity
      benchmark: electrical_resistivity
      line: The Goodfellow bar (99.95% purity) has a resistivity of 1.63 microohm cm at 20 °C with a temperature coefficient of 0.0041 per K.
    - label: Conduct heat
      benchmark: thermal_conductivity
      line: Thermal conductivity is 429 W/(m K) over 0 to 100 °C. Heat also makes silver expand by 19.1 ppm/K over the same range.
    - label: Reflect light
      value: About 98% at 400 to 1000 nm
      line: A silver-enhanced telescope coating averaged about 98% specular reflectivity from 400 to 1000 nm. This is a protected coating, not bare silver.
    - label: Carry load
      value: 172 to 330 MPa
      line: Tensile strength is 172 MPa soft and 330 MPa hard, Vickers hardness 25 and 95 kgf/mm2, and tensile modulus 82.7 GPa. Silver is a soft metal and is not used as a structure.
  compare: 'No opened source in this record compares silver with other metals on the same test, so no ranking is made here except the Wikipedia statement that silver has the highest electrical conductivity of all metals. Among silver coatings, the sulphur test showed thickness matters: the 86 nm, 130 nm and 200 nm layers gave very low, about 90% and about 97% average reflectivity.'
  handling:
    - Hazard classification depends on form; use the safety data sheet for bulk, powder or nano silver.
    - Bare silver tarnishes in sulphur-bearing air, so keep silver parts covered or protected.
    - In orbit, never leave silver facing atomic oxygen without a covering layer.
  good_for:
    - Conduction. A resistivity of 1.63 microohm cm and a thermal conductivity of 429 W/(m K) in the supplier table.
    - Reflection. A protected silver coating averaged about 98% specular reflectivity from 400 to 1000 nm.
    - Solar-cell contacts and interconnects. Silver was the last contact metal on GaAs cells in a TRW and JPL study.
  watch_out:
    - Atomic oxygen. Exposed silver forms a black oxide that cracks and spalls, and the Solar Maximum Mission blankets showed flaking.
    - Tarnish. Hydrogen sulphide forms Ag2S, which absorbs visible light and darkens bare silver.
    - Softness and weight. Density is 10.5 g/cm3 and soft silver has a tensile strength of 172 MPa.
    - Supply. Silver is mostly a byproduct of lead-zinc, copper and gold mining, and it was added to the US critical minerals list in 2025.
  verdict: Silver is the standard choice when conduction or reflection is needed, and spacecraft use it behind covering layers. Flight and ground data agree that bare silver in low Earth orbit oxidises quickly, so a design that exposes it needs protection, and the numeric rates for that attack are still missing from this record.
  compare_rows:
    - label: Density
      benchmark: density
      scope: material
    - label: Melting point
      benchmark: melting_point
      scope: material
    - label: Thermal conductivity
      benchmark: thermal_conductivity
      scope: material
  recipe:
    line: >-
      Silver is the element Ag, atomic number 47, a single-element metal with cubic close-packed crystals (ccp, space group Fm-3m, WebElements). USGS says silver is mostly obtained as a by-product of lead-zinc, copper and gold mines, and that its polymetallic ore deposits account for more than two-thirds of resources. In 2025, 24 US refiners produced commercial-grade silver from domestic and foreign ores, concentrates and scrap, with about 1,000 tons recovered from new and old scrap (USGS).
    parts:
      - name: Silver
        symbol: Ag
        atoms: 1
        atomic_weight: 107.8682
        role: "The whole material. WebElements prints the relative atomic mass on its main page."