{
  "spore": "profile",
  "id": "ule-glass",
  "spore_version": "0.2",
  "family": "glass-and-composites",
  "name": "ULE 7972 (Corning ultra low expansion titania-silicate glass)",
  "abbreviation": "ULE",
  "role": "low-expansion mirror blank and optical substrate",
  "category": "glasses-optics",
  "type": "fused-silica",
  "summary": "ULE 7972 is Corning's titania-silicate glass, sold as Corning Code 7972 ultra low expansion glass. Corning's product sheet guarantees a mean coefficient of thermal expansion of 0 ± 30 ppb/°C from 5 to 35 °C at a 95% confidence level, and prints a density of 2.21 g/cm3 at 25 °C. NASA Marshall names ULE among the materials used for space telescope mirrors, including the primary mirror of the Hubble Space Telescope.\n",
  "best_for": "Mirrors and precision parts that must hold their shape across temperature changes (guaranteed mean expansion of 0 ± 30 ppb/°C from 5 to 35 °C)",
  "weakest_at": "Brittle like other glasses: flawed ULE can fail under sustained tensile stress (delayed failure, NASA 2003), and the product sheet gives no fracture toughness",
  "identity": {
    "formula": "Titania-silicate glass: silica (SiO2) with about 7.5% titanium dioxide (TiO2) per NASA (2003); Wikipedia gives less than 10% TiO2",
    "designations": [
      {
        "system": "Trade name",
        "code": "ULE",
        "source": "corning-ule-datasheet",
        "where": "Title line: ULE Corning Code 7972 Ultra Low Expansion Glass"
      },
      {
        "system": "Trade name",
        "code": "7972",
        "note": "Corning code for ULE ultra low expansion glass",
        "source": "corning-ule-datasheet",
        "where": "Title line"
      }
    ],
    "source": "nasa-tucker2003",
    "where": "Abstract, sentence beginning 'ULE contains 7.5% titanium dioxide'"
  },
  "tags": {
    "environments": [],
    "stresses": [],
    "applications": [
      "optics-and-cameras",
      "electronics-and-chips",
      "structures"
    ]
  },
  "properties": [
    {
      "benchmark": "density",
      "label": "Density, ULE 7972",
      "value": 2.21,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "temperature": "25 °C (sheet default, unless otherwise stated all values are at 25 °C)"
      },
      "method": "Value printed on the Corning ULE 7972 product sheet as \"2.21 g/cm3 [0.079 lbs./in3]\"",
      "status": "ground",
      "source": "corning-ule-datasheet",
      "where": "Mechanical Properties block, Density (rho)",
      "source_detail": {
        "title": "Corning ULE 7972 Ultra Low Expansion Glass product sheet (Advanced Optics and Materials; Corning copyright 2006, supersedes August 2005), copy hosted by Light Machinery",
        "id": "ULE Corning Code 7972",
        "url": "https://lightmachinery.com/media/1556/ule-2006.pdf",
        "year": 2006,
        "kind": "datasheet",
        "license": "Manufacturer data sheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "cte",
      "label": "Mean coefficient of thermal expansion, ULE 7972 (guaranteed limit)",
      "value": 30,
      "bound": "upper",
      "unit": "ppb/°C",
      "scope": "material",
      "conditions": {
        "temperature_range": "5 to 35 °C",
        "confidence": "95%",
        "reading": "the sheet guarantees a mean of 0 ± 30 ppb/°C; the value is the ±30 limit"
      },
      "method": "Guaranteed limit printed on the Corning sheet as \"The mean CTE shall be 0 ± 30 ppb/°C from 5°C to 35°C with a 95% confidence level\"",
      "status": "ground",
      "note": "Read as a guaranteed limit on the mean, not a single measured value. Wikipedia gives a different form of the same small number (see the next row).",
      "source": "corning-ule-datasheet",
      "where": "Linear Coefficient of Thermal Expansion paragraph; Thermal Properties block, Mean coefficient of thermal expansion 5 to 35 C",
      "source_detail": {
        "title": "Corning ULE 7972 Ultra Low Expansion Glass product sheet (Advanced Optics and Materials; Corning copyright 2006, supersedes August 2005), copy hosted by Light Machinery",
        "id": "ULE Corning Code 7972",
        "url": "https://lightmachinery.com/media/1556/ule-2006.pdf",
        "year": 2006,
        "kind": "datasheet",
        "license": "Manufacturer data sheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "cte",
      "label": "Coefficient of thermal expansion quoted on Wikipedia",
      "value": 1e-8,
      "bound": "exact",
      "unit": "/K",
      "scope": "material",
      "conditions": {
        "temperature_range": "5 to 35 °C",
        "unit_in_source": "10−8/K"
      },
      "method": "Single figure printed on the Wikipedia article as 10−8/K for 5 to 35 °C",
      "status": "ground",
      "note": "Second-hand figure from an encyclopedia article. It agrees in order of magnitude with the Corning guarantee and is not used for any comparison here.",
      "source": "wiki-ule",
      "where": "Thermal section, coefficient of thermal expansion value",
      "source_detail": {
        "title": "Wikipedia: Ultra-low expansion glass (composition, history and CTE only)",
        "url": "https://en.wikipedia.org/wiki/Ultra_low_expansion_glass",
        "kind": "web",
        "license": "CC BY-SA (cited, not reproduced)"
      }
    },
    {
      "benchmark": "thermal_conductivity",
      "label": "Thermal conductivity, ULE 7972",
      "value": 1.31,
      "bound": "exact",
      "unit": "W/(m·°C)",
      "scope": "material",
      "conditions": {
        "temperature": "25 °C (sheet default)"
      },
      "method": "Value printed on the Corning ULE 7972 product sheet as \"1.31 w/(m • ºC) [1.31 kcal/(m • hr • ºC)]\"",
      "status": "ground",
      "note": "The PGO page and the AZoM table print the same 1.31 figure.",
      "source": "corning-ule-datasheet",
      "where": "Thermal Properties block, Thermal conductivity (K)",
      "source_detail": {
        "title": "Corning ULE 7972 Ultra Low Expansion Glass product sheet (Advanced Optics and Materials; Corning copyright 2006, supersedes August 2005), copy hosted by Light Machinery",
        "id": "ULE Corning Code 7972",
        "url": "https://lightmachinery.com/media/1556/ule-2006.pdf",
        "year": 2006,
        "kind": "datasheet",
        "license": "Manufacturer data sheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "specific_heat",
      "label": "Mean specific heat capacity, ULE 7972",
      "value": 767,
      "bound": "exact",
      "unit": "J/(kg·°C)",
      "scope": "material",
      "conditions": {
        "temperature": "25 °C (sheet default; the sheet gives a mean value without a temperature range)"
      },
      "method": "Value printed on the Corning ULE 7972 product sheet as \"767 J/ (kg • ºC) [0.183 cal/(g • ºC)]\"",
      "status": "ground",
      "source": "corning-ule-datasheet",
      "where": "Thermal Properties block, Mean specific heat (Cp)",
      "source_detail": {
        "title": "Corning ULE 7972 Ultra Low Expansion Glass product sheet (Advanced Optics and Materials; Corning copyright 2006, supersedes August 2005), copy hosted by Light Machinery",
        "id": "ULE Corning Code 7972",
        "url": "https://lightmachinery.com/media/1556/ule-2006.pdf",
        "year": 2006,
        "kind": "datasheet",
        "license": "Manufacturer data sheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "strain_point",
      "label": "Strain point, ULE 7972",
      "value": 890,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "basis": "as printed on the sheet, which gives 1634 °F alongside"
      },
      "method": "Value printed on the Corning ULE 7972 product sheet",
      "status": "ground",
      "note": "Non-canonical property name (strain_point); no canonical name exists in the property file.",
      "source": "corning-ule-datasheet",
      "where": "Thermal Properties block, Strain point",
      "source_detail": {
        "title": "Corning ULE 7972 Ultra Low Expansion Glass product sheet (Advanced Optics and Materials; Corning copyright 2006, supersedes August 2005), copy hosted by Light Machinery",
        "id": "ULE Corning Code 7972",
        "url": "https://lightmachinery.com/media/1556/ule-2006.pdf",
        "year": 2006,
        "kind": "datasheet",
        "license": "Manufacturer data sheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "annealing_point",
      "label": "Annealing point, ULE 7972",
      "value": 1000,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "basis": "as printed on the sheet, which gives 1832 °F alongside"
      },
      "method": "Value printed on the Corning ULE 7972 product sheet",
      "status": "ground",
      "note": "Non-canonical property name (annealing_point); no canonical name exists in the property file.",
      "source": "corning-ule-datasheet",
      "where": "Thermal Properties block, Annealing point",
      "source_detail": {
        "title": "Corning ULE 7972 Ultra Low Expansion Glass product sheet (Advanced Optics and Materials; Corning copyright 2006, supersedes August 2005), copy hosted by Light Machinery",
        "id": "ULE Corning Code 7972",
        "url": "https://lightmachinery.com/media/1556/ule-2006.pdf",
        "year": 2006,
        "kind": "datasheet",
        "license": "Manufacturer data sheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "softening_point",
      "label": "Softening point, ULE 7972 (estimated)",
      "value": 1490,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "basis": "printed by Corning as an estimated value, 2714 °F alongside"
      },
      "method": "Value printed on the Corning ULE 7972 product sheet, marked \"(estimated)\"",
      "status": "ground",
      "note": "Corning labels this value as estimated. Non-canonical property name (softening_point).",
      "source": "corning-ule-datasheet",
      "where": "Thermal Properties block, Softening point (estimated)",
      "source_detail": {
        "title": "Corning ULE 7972 Ultra Low Expansion Glass product sheet (Advanced Optics and Materials; Corning copyright 2006, supersedes August 2005), copy hosted by Light Machinery",
        "id": "ULE Corning Code 7972",
        "url": "https://lightmachinery.com/media/1556/ule-2006.pdf",
        "year": 2006,
        "kind": "datasheet",
        "license": "Manufacturer data sheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "elastic_modulus",
      "label": "Elastic (Young's) modulus, ULE 7972",
      "value": 67.6,
      "bound": "exact",
      "unit": "GPa",
      "scope": "material",
      "conditions": {
        "temperature": "25 °C (sheet default)"
      },
      "method": "Value printed on the Corning ULE 7972 product sheet as \"67.6 GPa [9.80 x 10 6 psi]\"",
      "status": "ground",
      "source": "corning-ule-datasheet",
      "where": "Mechanical Properties block, Elastic Modulus (E)",
      "source_detail": {
        "title": "Corning ULE 7972 Ultra Low Expansion Glass product sheet (Advanced Optics and Materials; Corning copyright 2006, supersedes August 2005), copy hosted by Light Machinery",
        "id": "ULE Corning Code 7972",
        "url": "https://lightmachinery.com/media/1556/ule-2006.pdf",
        "year": 2006,
        "kind": "datasheet",
        "license": "Manufacturer data sheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "shear_modulus",
      "label": "Shear modulus, ULE 7972",
      "value": 29,
      "bound": "exact",
      "unit": "GPa",
      "scope": "material",
      "conditions": {
        "temperature": "25 °C (sheet default)"
      },
      "method": "Value printed on the Corning ULE 7972 product sheet as \"29.0 GPa [4.20 x 10 6 psi]\"",
      "status": "ground",
      "source": "corning-ule-datasheet",
      "where": "Mechanical Properties block, Shear Modulus (G)",
      "source_detail": {
        "title": "Corning ULE 7972 Ultra Low Expansion Glass product sheet (Advanced Optics and Materials; Corning copyright 2006, supersedes August 2005), copy hosted by Light Machinery",
        "id": "ULE Corning Code 7972",
        "url": "https://lightmachinery.com/media/1556/ule-2006.pdf",
        "year": 2006,
        "kind": "datasheet",
        "license": "Manufacturer data sheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "bulk_modulus",
      "label": "Bulk modulus, ULE 7972",
      "value": 34.1,
      "bound": "exact",
      "unit": "GPa",
      "scope": "material",
      "conditions": {
        "temperature": "25 °C (sheet default)"
      },
      "method": "Value printed on the Corning ULE 7972 product sheet as \"34.1 GPa [4.95 x 10 6 psi]\"",
      "status": "ground",
      "source": "corning-ule-datasheet",
      "where": "Mechanical Properties block, Bulk Modulus (K)",
      "source_detail": {
        "title": "Corning ULE 7972 Ultra Low Expansion Glass product sheet (Advanced Optics and Materials; Corning copyright 2006, supersedes August 2005), copy hosted by Light Machinery",
        "id": "ULE Corning Code 7972",
        "url": "https://lightmachinery.com/media/1556/ule-2006.pdf",
        "year": 2006,
        "kind": "datasheet",
        "license": "Manufacturer data sheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "poissons_ratio",
      "label": "Poisson's ratio, ULE 7972",
      "value": 0.17,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "temperature": "25 °C (sheet default)"
      },
      "method": "Value printed on the Corning ULE 7972 product sheet",
      "status": "ground",
      "source": "corning-ule-datasheet",
      "where": "Mechanical Properties block, Poisson's ratio (nu)",
      "source_detail": {
        "title": "Corning ULE 7972 Ultra Low Expansion Glass product sheet (Advanced Optics and Materials; Corning copyright 2006, supersedes August 2005), copy hosted by Light Machinery",
        "id": "ULE Corning Code 7972",
        "url": "https://lightmachinery.com/media/1556/ule-2006.pdf",
        "year": 2006,
        "kind": "datasheet",
        "license": "Manufacturer data sheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "modulus_of_rupture",
      "label": "Modulus of rupture (MOR), as printed",
      "value": 49.8,
      "bound": "exact",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "basis": "printed as ultimate tensile stress with the abbreviation MOR (modulus of rupture); the sheet does not describe the test"
      },
      "method": "Value printed on the Corning ULE 7972 product sheet as \"49.8 MPa [7220 psi]\"",
      "status": "ground",
      "note": "The sheet labels this row Ultimate tensile stress (MOR) and gives no test method. MOR usually refers to a bend-test strength, so it is filed as modulus of rupture and not ranked as a tensile strength.",
      "source": "corning-ule-datasheet",
      "where": "Mechanical Properties block, Ultimate tensile stress (MOR)",
      "source_detail": {
        "title": "Corning ULE 7972 Ultra Low Expansion Glass product sheet (Advanced Optics and Materials; Corning copyright 2006, supersedes August 2005), copy hosted by Light Machinery",
        "id": "ULE Corning Code 7972",
        "url": "https://lightmachinery.com/media/1556/ule-2006.pdf",
        "year": 2006,
        "kind": "datasheet",
        "license": "Manufacturer data sheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "knoop_hardness",
      "label": "Knoop hardness, ULE 7972",
      "value": 460,
      "bound": "exact",
      "unit": "kg/mm2",
      "scope": "material",
      "conditions": {
        "load": "200 g"
      },
      "method": "Value printed on the Corning ULE 7972 product sheet as \"Knoop Hardness, 200 g load 460 kg/mm2\"",
      "status": "ground",
      "note": "AZoM prints 49 Knoop with no load or unit scale stated, which differs by about a factor of ten. Only the Corning value is recorded. Non-canonical property name (knoop_hardness).",
      "source": "corning-ule-datasheet",
      "where": "Mechanical Properties block, Knoop Hardness",
      "source_detail": {
        "title": "Corning ULE 7972 Ultra Low Expansion Glass product sheet (Advanced Optics and Materials; Corning copyright 2006, supersedes August 2005), copy hosted by Light Machinery",
        "id": "ULE Corning Code 7972",
        "url": "https://lightmachinery.com/media/1556/ule-2006.pdf",
        "year": 2006,
        "kind": "datasheet",
        "license": "Manufacturer data sheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "refractive_index",
      "label": "Refractive index nD, ULE 7972 (nominal CTE material)",
      "value": 1.4828,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "wavelength": "589 nm (nD)",
        "material": "nominal CTE material, as printed"
      },
      "method": "Value printed on the Corning ULE 7972 product sheet in the Optical Properties block",
      "status": "ground",
      "note": "The sheet also prints nF (486 nm) 1.4892 and nC (656 nm) 1.4801. The PGO page prints the same nD value.",
      "source": "corning-ule-datasheet",
      "where": "Optical Properties block, Refractive index nD (589 nm)",
      "source_detail": {
        "title": "Corning ULE 7972 Ultra Low Expansion Glass product sheet (Advanced Optics and Materials; Corning copyright 2006, supersedes August 2005), copy hosted by Light Machinery",
        "id": "ULE Corning Code 7972",
        "url": "https://lightmachinery.com/media/1556/ule-2006.pdf",
        "year": 2006,
        "kind": "datasheet",
        "license": "Manufacturer data sheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "abbe_number",
      "label": "Abbe number (vd), ULE 7972",
      "value": 53.1,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "notation": "vd, printed as Abbe' Number (vd)"
      },
      "method": "Value printed on the Corning ULE 7972 product sheet",
      "status": "ground",
      "note": "Non-canonical property name (abbe_number).",
      "source": "corning-ule-datasheet",
      "where": "Optical Properties block, Abbe Number (vd)",
      "source_detail": {
        "title": "Corning ULE 7972 Ultra Low Expansion Glass product sheet (Advanced Optics and Materials; Corning copyright 2006, supersedes August 2005), copy hosted by Light Machinery",
        "id": "ULE Corning Code 7972",
        "url": "https://lightmachinery.com/media/1556/ule-2006.pdf",
        "year": 2006,
        "kind": "datasheet",
        "license": "Manufacturer data sheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "thermal_diffusivity",
      "label": "Thermal diffusivity, ULE 7972",
      "value": 0.0079,
      "bound": "exact",
      "unit": "cm2/s",
      "scope": "material",
      "conditions": {
        "temperature": "not stated on the sheet (sheet default 25 °C)"
      },
      "method": "Value printed on the Corning ULE 7972 product sheet as \"0.0079 cm2/s\" (the sheet spells the label 'diffusity')",
      "status": "ground",
      "note": "PGO prints 0.079 cm2/s for the same property. The Corning figure is recorded here and the difference is not resolved. Non-canonical property name (thermal_diffusivity).",
      "source": "corning-ule-datasheet",
      "where": "Thermal Properties block, Thermal diffusity (D)",
      "source_detail": {
        "title": "Corning ULE 7972 Ultra Low Expansion Glass product sheet (Advanced Optics and Materials; Corning copyright 2006, supersedes August 2005), copy hosted by Light Machinery",
        "id": "ULE Corning Code 7972",
        "url": "https://lightmachinery.com/media/1556/ule-2006.pdf",
        "year": 2006,
        "kind": "datasheet",
        "license": "Manufacturer data sheet (cited, not reproduced)"
      }
    },
    {
      "benchmark": "dielectric_constant",
      "label": "Dielectric constant, ULE 7972",
      "value": 3.99,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "frequency": "100 Hz",
        "temperature": "25 °C"
      },
      "method": "Value printed on the PGO ULE page in the electrical properties list",
      "status": "ground",
      "source": "pgo-ule",
      "where": "Electrical properties list, Dielectric Constant",
      "source_detail": {
        "title": "PGO: ULE (Corning code 7972) properties page",
        "url": "https://www.pgo-online.com/intl/ule.html",
        "kind": "web",
        "license": "Web page (cited, not reproduced)"
      }
    },
    {
      "benchmark": "dissipation_factor",
      "label": "Loss factor (dissipation factor), ULE 7972",
      "value": 0.00005,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "frequency": "100 Hz",
        "temperature": "25 °C"
      },
      "method": "Value printed on the PGO ULE page as \"Loss Factor 0.00005\"",
      "status": "ground",
      "source": "pgo-ule",
      "where": "Electrical properties list, Loss Factor",
      "source_detail": {
        "title": "PGO: ULE (Corning code 7972) properties page",
        "url": "https://www.pgo-online.com/intl/ule.html",
        "kind": "web",
        "license": "Web page (cited, not reproduced)"
      }
    },
    {
      "benchmark": "max_service_temp",
      "label": "Maximum working temperature, ULE (blended table value)",
      "value": 800,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "basis": "printed as maximum working temperature in the AZoM table, with no condition given"
      },
      "method": "Value printed in the AZoM ULE property table as \"800 °C\"",
      "status": "ground",
      "note": "The Corning sheet gives no number; it says only 'High operating temperature'. The AZoM table states that its data are blended from multiple sources and are not warrantable.",
      "source": "azom-ule",
      "where": "Table 1, Maximum working temperature row",
      "source_detail": {
        "title": "AZoM: Ultra Low Expansion (ULE) glass, Table 1 Mechanical and Physical Properties for ULE",
        "id": "AZoM article ID 5911",
        "url": "https://www.azom.com/article.aspx?ArticleID=5911",
        "kind": "web",
        "license": "Web page (cited, not reproduced)"
      }
    }
  ],
  "corrosion": [
    {
      "environment": "5% hydrochloric acid, 95 °C, 24 hours",
      "headline": "Acid barely attacks ULE 7972: under 0.01 mg/cm2 lost in 24 hours at 95 °C.",
      "effect": "The Corning chemical durability table prints a weight loss below 0.01 mg/cm2 for 5% HCl after 24 hours at 95 °C.",
      "rating": "low",
      "conditions": {
        "solution": "5% HCl",
        "temperature": "95 °C",
        "duration": "24 h",
        "weight_loss_printed": "<0.01 mg/cm2"
      },
      "source": "corning-ule-datasheet",
      "where": "Chemical durability table, row 5% HCl"
    },
    {
      "environment": "5% sulphuric acid, 95 °C, 24 hours",
      "headline": "Sulphuric acid also barely attacks ULE 7972: under 0.01 mg/cm2 in 24 hours at 95 °C.",
      "effect": "The Corning table prints a weight loss below 0.01 mg/cm2 for 5% H2SO4 after 24 hours at 95 °C.",
      "rating": "low",
      "conditions": {
        "solution": "5% H2SO4",
        "temperature": "95 °C",
        "duration": "24 h",
        "weight_loss_printed": "<0.01 mg/cm2"
      },
      "source": "corning-ule-datasheet",
      "where": "Chemical durability table, row 5% H2SO4"
    },
    {
      "environment": "Water, 95 °C, 24 hours",
      "headline": "Hot water removes less than 0.01 mg/cm2 of ULE 7972 in 24 hours.",
      "effect": "The Corning table prints a weight loss below 0.01 mg/cm2 for water (H2O) after 24 hours at 95 °C.",
      "rating": "low",
      "conditions": {
        "solution": "H2O",
        "temperature": "95 °C",
        "duration": "24 h",
        "weight_loss_printed": "<0.01 mg/cm2"
      },
      "source": "corning-ule-datasheet",
      "where": "Chemical durability table, row H2O"
    },
    {
      "environment": "0.02 N sodium carbonate, 95 °C, 6 hours",
      "headline": "Dilute sodium carbonate removes 0.02 mg/cm2 of ULE 7972 in 6 hours at 95 °C.",
      "effect": "The Corning table prints a weight loss of 0.02 mg/cm2 for 0.02N Na2CO3 after 6 hours at 95 °C.",
      "rating": "low",
      "conditions": {
        "solution": "0.02N Na2CO3",
        "temperature": "95 °C",
        "duration": "6 h",
        "weight_loss_printed": "0.02 mg/cm2"
      },
      "source": "corning-ule-datasheet",
      "where": "Chemical durability table, row 0.02N Na2CO3"
    },
    {
      "environment": "5% sodium hydroxide, 95 °C, 6 hours",
      "headline": "Hot sodium hydroxide attacks ULE 7972 more than the acids and water in the table: 0.9 mg/cm2 in 6 hours at 95 °C.",
      "effect": "The Corning table prints a weight loss of 0.9 mg/cm2 for 5% NaOH after 6 hours at 95 °C, the largest loss in the table. The PGO page prints the same 0.90 mg/cm2 figure.",
      "rating": "moderate",
      "conditions": {
        "solution": "5% NaOH",
        "temperature": "95 °C",
        "duration": "6 h",
        "weight_loss_printed": "0.9 mg/cm2"
      },
      "source": "corning-ule-datasheet",
      "where": "Chemical durability table, row 5% NaOH"
    },
    {
      "environment": "Atmospheric weathering, water and sulphur dioxide",
      "headline": "Corning reports excellent weathering resistance and virtually no surface clouding.",
      "effect": "The sheet states excellent resistance to weathering and virtually no surface clouding or electrical surface leakage when exposed to water, sulfur dioxide and atmospheric gases. No number is given.",
      "rating": "low",
      "conditions": {
        "basis": "qualitative statement on the sheet; no test duration given"
      },
      "source": "corning-ule-datasheet",
      "where": "Chemical durability block, first bullet list"
    },
    {
      "environment": "Quench from 350 °C into water, and thermal cycling",
      "headline": "No figure change or measurable hysteresis reported after a 350 °C water quench or thermal cycling.",
      "effect": "The sheet states that a blank taken from 350 °C to a water quench shows no residual figure change, and that thermal cycling causes no measurable hysteresis at any rate of temperature change. It also reports no measurable delayed elastic effect.",
      "rating": "low",
      "conditions": {
        "basis": "qualitative statements on the sheet; no numbers given"
      },
      "source": "corning-ule-datasheet",
      "where": "Stability bullets on the Corning ULE 7972 sheet"
    }
  ],
  "risks": {
    "hazards": [
      {
        "text": "PubChem's titanium dioxide record (CID 26042) states that this chemical does not meet GHS hazard criteria in 62.8% (7032 of 11189) of company reports. Some notifications carry H351 (suspected of causing cancer) in 36.1% of reports that give hazard codes. The record covers titanium dioxide powder, not ULE glass, in which NASA says the titanium dioxide combines with silica into a homogeneous glass.",
        "ghs": [
          "H351"
        ],
        "source": "pubchem-tio2",
        "where": "Safety and Hazards, GHS Classification (CID 26042); ECHA C&L notification summary"
      }
    ],
    "failure_risks": [
      {
        "mode": "Delayed failure of flawed ULE under sustained tensile stress",
        "trigger": "Machined or ground flaws in the glass under sustained tensile stress",
        "consequence": "NASA MSFC measured dynamic fatigue on ULE and found that removing residual stress by grinding and polishing increased strength and lifetime. The authors note that a strength allowance based on modulus-of-rupture data ignores delayed failure, which can significantly shorten lifetime.",
        "severity": "moderate",
        "source": "nasa-tucker2003",
        "where": "Abstract"
      },
      {
        "mode": "Thermal distortion of a large space telescope mirror",
        "trigger": "Temperature changes across a mirror blank in orbit",
        "consequence": "A 1993 finite element estimate of thermally induced distortion in the Hubble primary mirror found that the distortion mainly produces defocus, with a relatively small contribution to spherical aberration. The paper's abstract gives no distortion figure.",
        "severity": "low",
        "source": "nasa-nied1993",
        "where": "Abstract"
      }
    ],
    "side_effects": [],
    "handling": [],
    "mitigations": [
      {
        "text": "NASA's 2003 tests found that grinding and polishing to a mirror finish, rather than a coarse 230/270 grit surface, removed residual stress and raised strength and lifetime.",
        "source": "nasa-tucker2003",
        "where": "Abstract"
      }
    ]
  },
  "uses": [
    {
      "application": "optics-and-cameras",
      "device": "Hubble Space Telescope primary mirror",
      "example": "NASA Marshall states that ULE is used where low thermal expansion matters, such as telescope mirrors, including the Hubble Space Telescope primary mirror.",
      "source": "nasa-tucker2003",
      "where": "Abstract"
    },
    {
      "application": "optics-and-cameras",
      "device": "1.5 m primary mirror for ultra-stable UVOIR space telescopes (ground model and test)",
      "example": "NASA MSFC describes a 1.5-meter ULE mirror, manufactured by Harris Corp, used to build a structural, thermal and optical performance model and to run bulk-temperature and lateral-gradient tests.",
      "source": "nasa-stahl2019",
      "where": "Abstract"
    },
    {
      "application": "electronics-and-chips",
      "device": "EUV lithography optics and substrates",
      "example": "Corning's product sheet says that industry experts in semiconductor manufacturing have identified ULE as a 'material of choice' for EUV applications (manufacturer statement).",
      "source": "corning-ule-datasheet",
      "where": "Introduction text"
    },
    {
      "application": "structures",
      "device": "Machine tool reference blocks",
      "example": "Corning's product sheet lists machine tool reference blocks among its applications, next to mirror blanks for large astronomical telescopes and space satellites.",
      "source": "corning-ule-datasheet",
      "where": "Introduction text"
    }
  ],
  "supply": [
    {
      "subject": "Titanium (as titanium dioxide, the titania in ULE)",
      "producers": [
        {
          "country": "China",
          "share_percent": 60.6,
          "year": 2025
        },
        {
          "country": "United States",
          "share_percent": 13.7,
          "year": 2025
        },
        {
          "country": "Mexico",
          "share_percent": 3.5,
          "year": 2025
        }
      ],
      "critical_lists": [
        {
          "list": "USGS 2025 List of Critical Minerals (titanium named as used as a white pigment and in metal alloys)",
          "listed": true
        }
      ],
      "substitutes": [],
      "source": "usgs-mcs2026-titanium",
      "where": "TiO2 pigment capacity, 2025e table (world total 9,900,000 t; shares calculated by Space Mushroom from China 6,000,000 t, United States 1,360,000 t and Mexico 350,000 t). Capacity, not mine production or ilmenite and rutile feedstock."
    },
    {
      "subject": "Silicon (silica from high-purity sand, the base of ULE)",
      "abundance": "USGS: world and domestic resources for making silicon metal and alloys are abundant and, in most producing countries, adequate to supply world requirements for many decades.",
      "producers": [
        {
          "country": "China",
          "share_percent": 80,
          "year": 2025
        }
      ],
      "critical_lists": [
        {
          "list": "USGS 2025 List of Critical Minerals",
          "listed": true
        }
      ],
      "recycling": "USGS silicon chapter: 'Insignificant.'",
      "substitutes": [],
      "source": "usgs-mcs2026-silicon",
      "where": "Events, Trends, and Issues ('almost 80%' of estimated global silicon-materials production in 2025, recorded as 80); World Resources; Recycling. The 80% covers silicon metal and ferrosilicon, not silica sand."
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "Corning ULE 7972 Ultra Low Expansion Glass product sheet (copy hosted by Light Machinery; Corning copyright 2006)",
      "type": "datasheet",
      "url": "https://lightmachinery.com/media/1556/ule-2006.pdf",
      "year": 2006
    },
    {
      "title": "NASA MSFC: Lifetime Predictions of a Titanium Silicate Glass with Machined Flaws (NTRS 20030062257)",
      "type": "paper",
      "url": "https://ntrs.nasa.gov/citations/20030062257",
      "year": 2003
    },
    {
      "title": "AIAA 93-0097: Temperature induced distortions in space telescope mirrors (NTRS 19930036205)",
      "type": "paper",
      "url": "https://ntrs.nasa.gov/citations/19930036205",
      "year": 1993
    },
    {
      "title": "NASA MSFC: Predictive Thermal Control Technology to Enable Thermally Stable Telescopes, first two year status (NTRS 20190029080)",
      "type": "paper",
      "url": "https://ntrs.nasa.gov/citations/20190029080",
      "year": 2019
    },
    {
      "title": "USGS Mineral Commodity Summaries 2026: Titanium and Titanium Dioxide",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-titanium.pdf",
      "year": 2026
    },
    {
      "title": "USGS Mineral Commodity Summaries 2026: Silicon",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf",
      "year": 2026
    },
    {
      "title": "PubChem: Titanium dioxide (CID 26042), Safety and Hazards",
      "type": "database",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/26042",
      "year": 2026
    }
  ],
  "gaps": [
    "Corning's own ULE 7972 PDFs and product page returned HTTP 403 to this run. The datasheet used is a 2006 copy hosted by Light Machinery, so a current Corning revision may print different values.",
    "No safety data sheet for ULE 7972 was found. The hazard entry uses PubChem's record for titanium dioxide powder, which is a substance-level caution and not a classification of the glass.",
    "No hydrofluoric acid or alkali-etch test for ULE 7972 was found in the sources read; the Corning sheet tests only the five solutions shown in the corrosion section.",
    "Maximum working temperature: the Corning sheet says only 'High operating temperature'. The 800 °C figure comes from the AZoM table, which says its data are blended from multiple sources and are not warrantable.",
    "Thermal diffusivity conflict: the Corning sheet prints 0.0079 cm2/s and PGO prints 0.079 cm2/s. The Corning figure is recorded and the conflict is not resolved.",
    "Hardness conflict: AZoM prints 49 Knoop with no load stated; the Corning sheet prints 460 kg/mm2 at 200 g load. Only the Corning value is recorded.",
    "Composition is not certified: NASA gives about 7.5% TiO2 and Wikipedia gives less than 10%. No source read gives the silica percentage.",
    "Corning's sheet and PGO print the thermal coefficient of refractive index (dn/dt: 10.68 x 10-6/°C at 20 to 40 °C and 11.24 x 10-6/°C at 40 to 60 °C) and the stress optical coefficient (4.15 (nm/cm)/(kg/cm3)). Neither is recorded because no canonical property name covers them.",
    "Electrical volume resistivity is printed on the Corning sheet, but the text extraction of the exponent was unclear, so it is not recorded.",
    "Outgassing (ASTM E595), atomic-oxygen and radiation behaviour of ULE 7972 were not looked up. No vacuum or flight result was read.",
    "Titanium feedstock (ilmenite and rutile mine production) not read: the USGS titanium mineral concentrates chapter URL returned HTML. Titanium shares here are pigment capacity.",
    "Silicon feedstock: high-purity silica sand production shares were not read. The 80% China figure covers silicon metal and ferrosilicon, not silica sand.",
    "Titanium recycling was not found in the titanium chapter read.",
    "No handling or storage guidance for ULE blanks was found in the sources read.",
    "The EU critical raw materials list was not checked for titanium or silicon.",
    "No measured thermal distortion or CTE map for the Hubble primary mirror was found. The 1993 NASA paper prints no CTE numbers in its abstract.",
    "Corrosion ratings (low, moderate) are Space Mushroom's judgement from the mg/cm2 figures; the Corning sheet does not rate them.",
    "Strain, annealing and softening points, Knoop hardness, Abbe number and thermal diffusivity use snake_case property names because no canonical name exists in the property file."
  ],
  "story": {
    "why": "ULE 7972 is a titania-silicate glass that Corning makes for precision optics, chosen because its thermal expansion is close to zero. Corning guarantees a mean coefficient of thermal expansion of 0 ± 30 ppb/°C from 5 to 35 °C at a 95% confidence level. Its density is 2.21 g/cm3 at 25 °C. NASA names ULE among the materials used for space telescope mirrors, including the Hubble Space Telescope primary mirror. The trade-off is brittleness: like other glasses, flawed ULE can fail under sustained tensile stress.",
    "uses": [
      {
        "where": "Space telescope mirrors",
        "line": "NASA Marshall names the Hubble Space Telescope primary mirror as an example of ULE in telescope optics. A later NASA model and test programme built a 1.5-metre ULE mirror to study thermal stability for ultra-stable space telescopes. That work is on the ground, and no in-orbit result for the new mirror is claimed here."
      },
      {
        "where": "EUV lithography",
        "line": "Corning says that industry experts in semiconductor manufacturing have identified ULE as a material of choice for EUV applications. This is a manufacturer's statement, and no independent test was read."
      },
      {
        "where": "Machine tool reference blocks",
        "line": "Corning lists machine tool reference blocks among the applications of ULE, next to mirror blanks for large astronomical telescopes and space satellites."
      }
    ],
    "can_do": [
      {
        "label": "Holds its size",
        "line": "Corning guarantees a mean coefficient of thermal expansion of 0 ± 30 ppb/°C from 5 to 35 °C at a 95% confidence level. Wikipedia gives 10−8/K for the same range.",
        "benchmark": "cte",
        "scope": "material",
        "value": "0 ± 30 ppb/°C mean, 5 to 35 °C"
      },
      {
        "label": "Stiff",
        "line": "The Young's modulus is 67.6 GPa at 25 °C, and the Poisson's ratio is 0.17, both as printed on the Corning sheet.",
        "benchmark": "elastic_modulus",
        "scope": "material",
        "value": "67.6 GPa"
      },
      {
        "label": "Bends light",
        "line": "The refractive index nD is 1.4828 at 589 nm for the nominal CTE material, and the Abbe number is 53.1.",
        "benchmark": "refractive_index",
        "scope": "material",
        "value": "1.4828 at 589 nm"
      },
      {
        "label": "Survives chemicals",
        "line": "The Corning table prints weight losses below 0.01 mg/cm2 for 5% HCl, 5% H2SO4 and water over 24 hours at 95 °C.",
        "scope": "material",
        "value": "under 0.01 mg/cm2 weight loss in 5% HCl, 24 h, 95 °C"
      }
    ],
    "compare": "Corning's sheet and the Wikipedia article both describe ULE as a glass with near-zero expansion, but state the figure differently: Corning guarantees a mean of 0 ± 30 ppb/°C from 5 to 35 °C, and Wikipedia gives 10−8/K for the same range. The two statements do not contradict each other. This profile does not compare ULE with fused silica or Zerodur, because those values were not read in this run.",
    "compare_rows": [
      {
        "label": "Mean thermal expansion",
        "benchmark": "cte",
        "scope": "material"
      },
      {
        "label": "Density",
        "benchmark": "density",
        "scope": "material"
      },
      {
        "label": "Thermal conductivity",
        "benchmark": "thermal_conductivity",
        "scope": "material"
      }
    ],
    "handling": [
      "No handling or storage guidance for ULE blanks was found in the sources read.",
      "NASA's 2003 study found that grinding and polishing removed residual stress and lengthened lifetime, so finishing matters for the life of a flawed blank."
    ],
    "good_for": [
      "Mirror blanks that must hold their shape over temperature changes: Corning guarantees a mean expansion of 0 ± 30 ppb/°C from 5 to 35 °C.",
      "EUV lithography parts, which Corning says industry experts identify as a material of choice (a manufacturer statement)."
    ],
    "watch_out": [
      "Delayed failure: NASA shows that flawed ULE can fail under sustained stress, and that a modulus-of-rupture strength allowance ignores this.",
      "Conflicting figures: thermal diffusivity (0.0079 vs 0.079 cm2/s) and hardness (460 kg/mm2 at 200 g vs 49 Knoop) differ between sources. See gaps.",
      "Composition is not certified: NASA gives 7.5% titanium dioxide and Wikipedia gives less than 10%."
    ],
    "verdict": "ULE 7972 is the low-expansion glass that NASA names for the Hubble primary mirror, and its guaranteed mean expansion of 0 ± 30 ppb/°C from 5 to 35 °C is the number to design against. The values here come from a 2006 Corning sheet copy and secondary tables, so check the current Corning revision before a flight design.",
    "recipe": {
      "line": "ULE 7972 is a titania-silicate glass: silica (SiO2) with about 7.5% titanium dioxide (TiO2), per the NASA Marshall 2003 paper. Wikipedia says the glass contains less than 10% titanium dioxide. NASA says the titanium dioxide combines with silica into a homogeneous glass with a near-zero linear expansion. Corning's product sheet does not print a composition.",
      "parts": [
        {
          "name": "Silica",
          "symbol": "SiO2",
          "role": "The glass network. Silica makes up the rest of the glass, and the titanium dioxide is combined with it to form one homogeneous glass.",
          "share_note": "Balance of the glass; no source read gives the silica percentage",
          "source": "nasa-tucker2003",
          "where": "Abstract, sentence on the composition"
        },
        {
          "name": "Titanium dioxide",
          "symbol": "TiO2",
          "role": "The additive that brings the thermal expansion close to zero. The NASA abstract says the titanium dioxide and silica together form a homogeneous glass with a near-zero linear expansion.",
          "share_percent": 7.5,
          "share_note": "NASA 2003 figure; Wikipedia gives less than 10%",
          "source": "nasa-tucker2003",
          "where": "Abstract, sentence beginning ULE contains 7.5% titanium dioxide"
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "Corning describes ULE 7972 as highly resistant to nearly all chemical agents, and its product sheet prints no hazard classification. The one caution comes from PubChem's titanium dioxide record, which is for powder.",
        "points": [
          {
            "label": "The glass",
            "line": "Corning's chemical durability table shows weight losses below 0.01 mg/cm2 for the acids and water tested at 95 °C, and 0.9 mg/cm2 for 5% sodium hydroxide over 6 hours."
          },
          {
            "label": "Titanium dioxide",
            "line": "PubChem's titanium dioxide record says 62.8% of company reports find it does not meet GHS hazard criteria, and 36.1% of reports that give hazard codes carry H351, suspected of causing cancer. This describes the powder, not the glass."
          }
        ],
        "level": 1,
        "verdict": "Dust caution only"
      },
      {
        "title": "If a blank fails",
        "lead": "NASA's 2003 study of ULE found that flaws and sustained tensile stress set the failure path, and that a strength value based on modulus of rupture can overstate lifetime.",
        "points": [
          {
            "label": "Flaws",
            "line": "Grinding and polishing to a mirror finish removed residual stress and raised strength and lifetime compared with a coarse 230/270 grit surface, per NASA MSFC."
          },
          {
            "label": "Stress",
            "line": "NASA notes that a strength allowance based on modulus-of-rupture data ignores delayed failure, which can significantly shorten lifetime."
          }
        ],
        "level": 2,
        "verdict": "Delayed failure of flawed blanks"
      },
      {
        "title": "Thermal behaviour",
        "lead": "The Corning sheet reports no residual change in the mirror figure after a quench from 350 °C and no measurable hysteresis from thermal cycling. These are qualitative statements with no numbers.",
        "points": [
          {
            "label": "Thermal cycling",
            "line": "Corning reports no measurable hysteresis from thermal cycling at any rate of temperature change, and no measurable delayed elastic effect."
          }
        ],
        "level": 0,
        "verdict": "No hysteresis reported"
      }
    ]
  },
  "updated": "2026-11-01",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 20,
    "unreachable": 3,
    "caveats": 2,
    "note": "Read by an AI assistant on 2026-11-01 from the Light Machinery copy of the 2006 Corning ULE 7972 product sheet, the PGO and AZoM property pages, the Wikipedia article, three NASA NTRS records, two USGS Mineral Commodity Summaries 2026 chapters, the USGS 2025 critical minerals page and the PubChem titanium dioxide record. Corning's own PDFs and product page returned HTTP 403. The PGO and AZoM pages are secondary and carry conflicts noted above."
  },
  "sources": {
    "corning-ule-datasheet": {
      "title": "Corning ULE 7972 Ultra Low Expansion Glass product sheet (Advanced Optics and Materials; Corning copyright 2006, supersedes August 2005), copy hosted by Light Machinery",
      "id": "ULE Corning Code 7972",
      "url": "https://lightmachinery.com/media/1556/ule-2006.pdf",
      "year": 2006,
      "kind": "datasheet",
      "license": "Manufacturer data sheet (cited, not reproduced)"
    },
    "pgo-ule": {
      "title": "PGO: ULE (Corning code 7972) properties page",
      "url": "https://www.pgo-online.com/intl/ule.html",
      "kind": "web",
      "license": "Web page (cited, not reproduced)"
    },
    "azom-ule": {
      "title": "AZoM: Ultra Low Expansion (ULE) glass, Table 1 Mechanical and Physical Properties for ULE",
      "id": "AZoM article ID 5911",
      "url": "https://www.azom.com/article.aspx?ArticleID=5911",
      "kind": "web",
      "license": "Web page (cited, not reproduced)"
    },
    "wiki-ule": {
      "title": "Wikipedia: Ultra-low expansion glass (composition, history and CTE only)",
      "url": "https://en.wikipedia.org/wiki/Ultra_low_expansion_glass",
      "kind": "web",
      "license": "CC BY-SA (cited, not reproduced)"
    },
    "nasa-tucker2003": {
      "title": "Tucker, Nettles and Cagle (NASA MSFC): Lifetime Predictions of a Titanium Silicate Glass with Machined Flaws",
      "id": "NTRS 20030062257",
      "url": "https://ntrs.nasa.gov/citations/20030062257",
      "year": 2003,
      "kind": "paper",
      "license": "NASA public document (cited, not reproduced)"
    },
    "nasa-nied1993": {
      "title": "Nied and Rudmann: Temperature induced distortions in space telescope mirrors (AIAA 93-0097)",
      "id": "NTRS 19930036205",
      "url": "https://ntrs.nasa.gov/citations/19930036205",
      "year": 1993,
      "kind": "paper",
      "license": "NASA public document (cited, not reproduced)"
    },
    "nasa-stahl2019": {
      "title": "Stahl and Brooks (NASA MSFC): Predictive Thermal Control Technology to Enable Thermally Stable Telescopes, first two year status",
      "id": "NTRS 20190029080",
      "url": "https://ntrs.nasa.gov/citations/20190029080",
      "year": 2019,
      "kind": "paper",
      "license": "NASA public document (cited, not reproduced)"
    },
    "usgs-mcs2026-titanium": {
      "title": "USGS Mineral Commodity Summaries 2026: Titanium and Titanium Dioxide",
      "id": "USGS MCS 2026, February 2026",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-titanium.pdf",
      "year": 2026,
      "kind": "report",
      "license": "US government publication (cited, not reproduced)"
    },
    "usgs-mcs2026-silicon": {
      "title": "USGS 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": "US government publication (cited, not reproduced)"
    },
    "usgs-crit2025": {
      "title": "USGS: About the 2025 List of Critical Minerals (final list of 60 minerals; titanium and silicon included)",
      "id": "Final 2025 List of Critical Minerals, November 2025",
      "url": "https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals",
      "year": 2025,
      "kind": "web",
      "license": "US government publication (cited, not reproduced)"
    },
    "pubchem-tio2": {
      "title": "PubChem compound record: Titanium dioxide (CID 26042), Safety and Hazards",
      "id": "CID 26042",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/26042",
      "year": 2026,
      "kind": "database",
      "license": "Public database (cited, not reproduced)"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/ule-glass/"
}