{
  "spore": "profile",
  "id": "boron-carbide",
  "spore_version": "0.2",
  "family": "carbide-nitride-boride-ceramics",
  "name": "Boron carbide",
  "abbreviation": "B4C",
  "role": "extremely hard ceramic for armor, wear parts and neutron shielding",
  "category": "ceramics",
  "type": "carbides",
  "summary": "Boron carbide is a boron-carbon ceramic, nominally B4C, and one of the hardest materials known. Saint-Gobain's hot-pressed Norbide datasheet gives a density of 2.50 gm/cm3, a Knoop hardness of 2800 kg/mm2, a four-point flexural strength of 425 MPa and an elastic modulus of 440 GPa, with a thermal conductivity of 90 W/mK at 20 °C. NIST's JANAF table gives a standard enthalpy of formation of -62.676 kJ/mol at 298.15 K. CoorsTek's table gives wider ranges for its hot-pressed grade, so the ranges are kept.\n",
  "best_for": "Hard, wear-resistant parts such as blast nozzles and armor tiles, and neutron shielding where boron content matters (Saint-Gobain datasheet; NASA 2023 composite study)",
  "weakest_at": "Brittleness: flexural strength of 425 MPa and fracture toughness of 3.1 MPa x m1/2 (Saint-Gobain), and loss of quality and hardness in hot air with traces of nitrogen (Varadachari et al. 2018)",
  "identity": {
    "formula": "B4C, a boron-carbon compound; the material is a family of compositions from boron-rich to carbon-rich (Wikipedia)",
    "cas": "12069-32-8",
    "designations": [],
    "source": "pubchem-b4c",
    "where": "Names and Identifiers of PubChem CID 123279: CAS 12069-32-8 and molecular formula CB4; the supplier SDS gives the same CAS"
  },
  "tags": {
    "environments": [],
    "stresses": [
      "extreme-heat"
    ],
    "applications": [
      "radiation-shielding",
      "structures",
      "mechanisms"
    ]
  },
  "properties": [
    {
      "benchmark": "density",
      "label": "Density, hot-pressed B4C (Norbide)",
      "value": 2.5,
      "bound": "exact",
      "unit": "gm/cm3",
      "scope": "material",
      "conditions": {
        "material": "Norbide hot pressed boron carbide"
      },
      "method": "Typical physical properties table of the Saint-Gobain datasheet (method not stated)",
      "status": "ground",
      "source": "sg-norbide-hp",
      "where": "Norbide Hot Pressed B4C Typical Physical Properties table, Density row",
      "source_detail": {
        "title": "Saint-Gobain Ceramics, Norbide Hot Pressed Boron Carbide Technical Data (Form No. B-1050, 11/04)",
        "url": "https://www.ceramicsrefractories.saint-gobain.com/fr/files/3956/view",
        "kind": "datasheet",
        "license": "vendor datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "knoop_hardness",
      "label": "Knoop hardness, hot-pressed B4C",
      "value": 2800,
      "bound": "exact",
      "unit": "kg/mm2",
      "scope": "material",
      "conditions": {
        "load": "Knoop 0.1 kg",
        "material": "Norbide hot pressed"
      },
      "method": "Knoop hardness as printed; Knoop is not Vickers, so it is not comparable with Vickers values",
      "status": "ground",
      "source": "sg-norbide-hp",
      "where": "Typical Physical Properties table, Hardness (Knoop) row, footnote 2",
      "source_detail": {
        "title": "Saint-Gobain Ceramics, Norbide Hot Pressed Boron Carbide Technical Data (Form No. B-1050, 11/04)",
        "url": "https://www.ceramicsrefractories.saint-gobain.com/fr/files/3956/view",
        "kind": "datasheet",
        "license": "vendor datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "flexural_strength",
      "label": "Flexural strength, 4-point, hot-pressed B4C (Saint-Gobain)",
      "value": 425,
      "bound": "exact",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "temperature": "room temperature",
        "test_bar": "3 x 4 x 45 mm",
        "material": "Norbide hot pressed"
      },
      "method": "Four-point bend on the test bar size given in the datasheet footnote",
      "status": "ground",
      "source": "sg-norbide-hp",
      "where": "Typical Physical Properties table, Flexural Strength 4pt @ RT row, footnote 3",
      "source_detail": {
        "title": "Saint-Gobain Ceramics, Norbide Hot Pressed Boron Carbide Technical Data (Form No. B-1050, 11/04)",
        "url": "https://www.ceramicsrefractories.saint-gobain.com/fr/files/3956/view",
        "kind": "datasheet",
        "license": "vendor datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "compressive_strength",
      "label": "Compressive strength, hot-pressed B4C",
      "value": 2900,
      "bound": "exact",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "temperature": "room temperature",
        "material": "Norbide hot pressed"
      },
      "method": "Compressive strength as printed in the datasheet (method not stated)",
      "status": "ground",
      "source": "sg-norbide-hp",
      "where": "Typical Physical Properties table, Compressive Strength @ RT row",
      "source_detail": {
        "title": "Saint-Gobain Ceramics, Norbide Hot Pressed Boron Carbide Technical Data (Form No. B-1050, 11/04)",
        "url": "https://www.ceramicsrefractories.saint-gobain.com/fr/files/3956/view",
        "kind": "datasheet",
        "license": "vendor datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "elastic_modulus",
      "label": "Elastic modulus, hot-pressed B4C",
      "value": 440,
      "bound": "exact",
      "unit": "GPa",
      "scope": "material",
      "conditions": {
        "temperature": "room temperature",
        "material": "Norbide hot pressed"
      },
      "method": "Modulus of elasticity as printed in the datasheet (method not stated)",
      "status": "ground",
      "source": "sg-norbide-hp",
      "where": "Typical Physical Properties table, Modulus of Elasticity @ RT row",
      "source_detail": {
        "title": "Saint-Gobain Ceramics, Norbide Hot Pressed Boron Carbide Technical Data (Form No. B-1050, 11/04)",
        "url": "https://www.ceramicsrefractories.saint-gobain.com/fr/files/3956/view",
        "kind": "datasheet",
        "license": "vendor datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "poissons_ratio",
      "label": "Poisson's ratio, hot-pressed B4C",
      "value": 0.18,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "material": "Norbide hot pressed"
      },
      "method": "Poisson's ratio as printed in the datasheet",
      "status": "ground",
      "source": "sg-norbide-hp",
      "where": "Typical Physical Properties table, Poisson's Ratio row",
      "source_detail": {
        "title": "Saint-Gobain Ceramics, Norbide Hot Pressed Boron Carbide Technical Data (Form No. B-1050, 11/04)",
        "url": "https://www.ceramicsrefractories.saint-gobain.com/fr/files/3956/view",
        "kind": "datasheet",
        "license": "vendor datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "fracture_toughness",
      "label": "Fracture toughness, indentation, hot-pressed B4C (Saint-Gobain)",
      "value": 3.1,
      "bound": "exact",
      "unit": "MPa x m1/2",
      "scope": "material",
      "conditions": {
        "temperature": "room temperature",
        "method_detail": "indentation"
      },
      "method": "Indentation fracture toughness as printed in the datasheet",
      "status": "ground",
      "source": "sg-norbide-hp",
      "where": "Typical Physical Properties table, Fracture Toughness @ RT (Indentation) row",
      "source_detail": {
        "title": "Saint-Gobain Ceramics, Norbide Hot Pressed Boron Carbide Technical Data (Form No. B-1050, 11/04)",
        "url": "https://www.ceramicsrefractories.saint-gobain.com/fr/files/3956/view",
        "kind": "datasheet",
        "license": "vendor datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "cte",
      "label": "Coefficient of thermal expansion, hot-pressed B4C (Saint-Gobain)",
      "value": 5,
      "bound": "exact",
      "unit": "x10-6 mm/mmK",
      "scope": "material",
      "conditions": {
        "material": "Norbide hot pressed",
        "temperature": "not stated in the table"
      },
      "method": "CTE as printed; the datasheet unit is x10-6 mm/mmK, kept as printed",
      "status": "ground",
      "source": "sg-norbide-hp",
      "where": "Typical Physical Properties table, Coefficient of Thermal Expansion row",
      "source_detail": {
        "title": "Saint-Gobain Ceramics, Norbide Hot Pressed Boron Carbide Technical Data (Form No. B-1050, 11/04)",
        "url": "https://www.ceramicsrefractories.saint-gobain.com/fr/files/3956/view",
        "kind": "datasheet",
        "license": "vendor datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "thermal_conductivity",
      "label": "Thermal conductivity, hot-pressed B4C (Saint-Gobain)",
      "value": 90,
      "bound": "exact",
      "unit": "W/mK",
      "scope": "material",
      "conditions": {
        "temperature": "20 °C",
        "material": "Norbide hot pressed"
      },
      "method": "Thermal conductivity as printed in the datasheet",
      "status": "ground",
      "source": "sg-norbide-hp",
      "where": "Typical Physical Properties table, Thermal Conductivity @20°C row",
      "source_detail": {
        "title": "Saint-Gobain Ceramics, Norbide Hot Pressed Boron Carbide Technical Data (Form No. B-1050, 11/04)",
        "url": "https://www.ceramicsrefractories.saint-gobain.com/fr/files/3956/view",
        "kind": "datasheet",
        "license": "vendor datasheet, cited not reproduced"
      }
    },
    {
      "benchmark": "flexural_strength",
      "label": "Flexural strength (MOR), hot-pressed B4C (CoorsTek)",
      "value": 320,
      "value_high": 450,
      "bound": "range",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "temperature": "20 °C",
        "grade": "hot pressed boron carbide"
      },
      "method": "Flexural Strength, MOR (20 °C) row, Hot Pressed column; printed as 320 - 450",
      "status": "ground",
      "source": "coors-b4c",
      "where": "Boron carbide properties table, Flexural Strength MOR (20 °C) row, Hot Pressed column",
      "source_detail": {
        "title": "CoorsTek, Boron Carbide material properties table (reaction bonded, hot pressed, sintered)",
        "url": "https://coorstek.com/en/materials/boron-carbide/",
        "kind": "web",
        "license": "vendor web page, cited not reproduced"
      }
    },
    {
      "benchmark": "fracture_toughness",
      "label": "Fracture toughness K Ic, hot-pressed B4C (CoorsTek)",
      "value": 3,
      "value_high": 4,
      "bound": "range",
      "unit": "MPa m 1/2",
      "scope": "material",
      "conditions": {
        "grade": "hot pressed boron carbide",
        "method_detail": "K Ic"
      },
      "method": "Fracture Toughness K Ic row, Hot Pressed column; printed as 3.0 - 4.0",
      "status": "ground",
      "source": "coors-b4c",
      "where": "Boron carbide properties table, Fracture Toughness K Ic row, Hot Pressed column",
      "source_detail": {
        "title": "CoorsTek, Boron Carbide material properties table (reaction bonded, hot pressed, sintered)",
        "url": "https://coorstek.com/en/materials/boron-carbide/",
        "kind": "web",
        "license": "vendor web page, cited not reproduced"
      }
    },
    {
      "benchmark": "thermal_conductivity",
      "label": "Thermal conductivity, hot-pressed B4C (CoorsTek)",
      "value": 45,
      "value_high": 100,
      "bound": "range",
      "unit": "W/m K",
      "scope": "material",
      "conditions": {
        "temperature": "20 °C",
        "grade": "hot pressed boron carbide"
      },
      "method": "Thermal Conductivity (20 °C) row, Hot Pressed column; printed as 45 - 100",
      "status": "ground",
      "source": "coors-b4c",
      "where": "Boron carbide properties table, Thermal Conductivity (20 °C) row, Hot Pressed column",
      "source_detail": {
        "title": "CoorsTek, Boron Carbide material properties table (reaction bonded, hot pressed, sintered)",
        "url": "https://coorstek.com/en/materials/boron-carbide/",
        "kind": "web",
        "license": "vendor web page, cited not reproduced"
      }
    },
    {
      "benchmark": "cte",
      "label": "Coefficient of thermal expansion, hot-pressed B4C (CoorsTek)",
      "value": 4.5,
      "value_high": 4.9,
      "bound": "range",
      "unit": "1x10 -6 /°C",
      "scope": "material",
      "conditions": {
        "grade": "hot pressed boron carbide"
      },
      "method": "Coefficient of Thermal Expansion row, Hot Pressed column; printed as 4.5 - 4.9 under a unit header of 1x10 -6 /°C",
      "status": "ground",
      "source": "coors-b4c",
      "where": "Boron carbide properties table, Coefficient of Thermal Expansion row, Hot Pressed column",
      "source_detail": {
        "title": "CoorsTek, Boron Carbide material properties table (reaction bonded, hot pressed, sintered)",
        "url": "https://coorstek.com/en/materials/boron-carbide/",
        "kind": "web",
        "license": "vendor web page, cited not reproduced"
      }
    },
    {
      "benchmark": "molar_heat_capacity",
      "label": "Molar heat capacity Cp, B4C, 298.15 K",
      "value": 53.764,
      "bound": "exact",
      "unit": "J K-1 mol-1",
      "scope": "material",
      "conditions": {
        "temperature": "298.15 K",
        "reference_state": "standard state pressure 0.1 MPa",
        "phase": "crystalline (cr)"
      },
      "method": "JANAF table value at 298.15 K; the column headings in the fetched page are partly garbled, so the column is mapped from the table layout",
      "status": "ground",
      "source": "janaf-b4c",
      "where": "Boron Carbide (B4C) table, row 298.15 K, Cp column",
      "source_detail": {
        "title": "NIST-JANAF Thermochemical Tables, Boron Carbide (B4C), table C-010",
        "url": "https://janaf.nist.gov/tables/C-010.html",
        "kind": "database",
        "license": "NIST public data"
      }
    },
    {
      "benchmark": "standard_molar_entropy",
      "label": "Standard molar entropy S, B4C, 298.15 K",
      "value": 27.175,
      "bound": "exact",
      "unit": "J K-1 mol-1",
      "scope": "material",
      "conditions": {
        "temperature": "298.15 K",
        "reference_state": "standard state pressure 0.1 MPa",
        "phase": "crystalline (cr)"
      },
      "method": "JANAF table value at 298.15 K; column mapped from the table layout, as for Cp",
      "status": "ground",
      "source": "janaf-b4c",
      "where": "Boron Carbide (B4C) table, row 298.15 K, S column",
      "source_detail": {
        "title": "NIST-JANAF Thermochemical Tables, Boron Carbide (B4C), table C-010",
        "url": "https://janaf.nist.gov/tables/C-010.html",
        "kind": "database",
        "license": "NIST public data"
      }
    },
    {
      "benchmark": "standard_enthalpy_of_formation",
      "label": "Standard enthalpy of formation, B4C, 298.15 K",
      "value": -62.676,
      "bound": "exact",
      "unit": "kJ mol-1",
      "scope": "material",
      "conditions": {
        "temperature": "298.15 K",
        "reference_state": "standard state pressure 0.1 MPa",
        "phase": "crystalline (cr)"
      },
      "method": "JANAF table value at 298.15 K; column mapped from the table layout, as for Cp",
      "status": "ground",
      "source": "janaf-b4c",
      "where": "Boron Carbide (B4C) table, row 298.15 K, Delta fH column",
      "source_detail": {
        "title": "NIST-JANAF Thermochemical Tables, Boron Carbide (B4C), table C-010",
        "url": "https://janaf.nist.gov/tables/C-010.html",
        "kind": "database",
        "license": "NIST public data"
      }
    }
  ],
  "corrosion": [
    {
      "environment": "Air or oxygen at elevated temperature",
      "headline": "A B2O3 surface layer forms first and shields the carbide from catastrophic oxidation, according to a 2018 thermodynamic study",
      "effect": "Varadachari, Bhowmick and Ghosh (2018) say the B2O3 that forms first acts as a protective shield, that oxidation reactions with O2 have positive log k values, and that the trioxide-producing reactions are the most energetically favoured. The region covered is 273 to 2300 K. The abstract gives no oxidation rates.",
      "rating": "unknown",
      "conditions": {
        "temperature": "273 to 2300 K, as the study gives it",
        "atmosphere": "O2 and N2"
      },
      "source": "zenodo-b4c-oxidation",
      "where": "Abstract, Description section"
    },
    {
      "environment": "Air containing traces of nitrogen",
      "headline": "Oxidation and nitrogen reactions affect the quality and hardness of the product",
      "effect": "The abstract says oxidative processes and reaction with traces of nitrogen in air affect the quality and hardness of the product. BN forms at the lowest temperatures and is stable at higher temperatures, according to the same study.",
      "rating": "unknown",
      "conditions": {
        "atmosphere": "air with traces of nitrogen"
      },
      "source": "zenodo-b4c-oxidation",
      "where": "Abstract, Description section"
    },
    {
      "environment": "Very low oxygen pressure and high concentrations of gaseous components",
      "headline": "B4C is stable only under extremely low O2 pressures in the study's conditions",
      "effect": "The abstract says B4C is stable only at extremely low O2 pressures and under high concentrations of gaseous components. No numeric pressure boundary is given.",
      "rating": "unknown",
      "conditions": {
        "atmosphere": "extremely low O2 pressure, high concentration of gaseous components"
      },
      "source": "zenodo-b4c-oxidation",
      "where": "Abstract, Description section"
    }
  ],
  "risks": {
    "hazards": [
      {
        "text": "PubChem aggregated GHS for boron carbide (CID 123279, signal word Danger): H360 and H360FD, reproductive toxicity, each notified by 19.5 percent of 185 company reports. 77.8 percent of reports (144 of 185) say it does not meet GHS criteria.",
        "ghs": [
          "H360",
          "H360FD"
        ],
        "source": "pubchem-b4c",
        "where": "Safety and Hazards, GHS Classification"
      },
      {
        "text": "Supplier SDS (Stanford Advanced Materials, revised 10/11/2022): signal word Warning, with H332 harmful if inhaled, H315 causes skin irritation, H319 causes serious eye irritation and H335 may cause respiratory irritation.",
        "ghs": [
          "H332",
          "H315",
          "H319",
          "H335"
        ],
        "source": "sds-stanford-b4c",
        "where": "Section 2, Hazards identification, Label elements"
      }
    ],
    "failure_risks": [
      {
        "mode": "Brittle fracture under tensile or bending load",
        "trigger": "Mechanical load on a flaw or machining damage",
        "consequence": "Four-point flexural strength of 425 MPa and indentation fracture toughness of 3.1 MPa x m1/2 for hot-pressed B4C",
        "severity": "moderate",
        "source": "sg-norbide-hp",
        "where": "Typical Physical Properties table, Flexural Strength and Fracture Toughness rows"
      },
      {
        "mode": "Loss of quality and hardness from oxidation and nitrogen reactions in hot air",
        "trigger": "Heating in air, including traces of nitrogen",
        "consequence": "The 2018 study says oxidative processes and reaction with traces of nitrogen in air affect the quality and hardness of the product",
        "severity": "moderate",
        "source": "zenodo-b4c-oxidation",
        "where": "Abstract, Description section"
      }
    ],
    "side_effects": [],
    "handling": [
      {
        "text": "Dust: PubChem's reproductive-toxicity entries (H360 and H360FD) and the supplier's inhalation statements (H332, H335) mean fine dust from grinding or machining should be controlled.",
        "source": "sds-stanford-b4c",
        "where": "Section 2, Hazards identification (H332, H335)"
      },
      {
        "text": "Storage and disposal: the SDS gives P405, store locked up, and P501, dispose of contents under local regulations.",
        "source": "sds-stanford-b4c",
        "where": "Section 2, Precautionary statements"
      }
    ],
    "mitigations": []
  },
  "uses": [
    {
      "application": "radiation-shielding",
      "device": "B4C particles in an aluminium alloy 6061 metal matrix composite for neutron shielding",
      "example": "NASA's 2023 Langley study reports that 50 vol percent B4C in Al6061 raised neutron shielding effectiveness more than 110 times over pristine Al6061. The abstract says tensile strength rose up to 20 vol percent and thermal conductivity fell as B4C content rose.",
      "source": "ntrs-20230003044",
      "where": "Abstract"
    },
    {
      "application": "structures",
      "device": "Hot-pressed B4C ballistic armor tiles",
      "example": "Saint-Gobain lists ballistic armor tiles and wear-resistant components among the applications of Norbide hot-pressed boron carbide, and calls the material one of the hardest known.",
      "source": "sg-norbide-hp",
      "where": "Product Description and Applications list"
    },
    {
      "application": "mechanisms",
      "device": "Wear-resistant nozzles, including grit-blast slurry nozzles",
      "example": "Saint-Gobain lists blast nozzles, monument nozzles and nozzles for grit blasting slurry among the applications of Norbide hot-pressed boron carbide.",
      "source": "sg-norbide-hp",
      "where": "Product Description and Applications list"
    }
  ],
  "supply": [
    {
      "subject": "Boron (feedstock for the boron half of B4C)",
      "abundance": "USGS 2026: boron does not occur in nature as an element. It is sold as borates and boric oxide. The production table lists Turkey at 1,800 (2024) and 1,500 (2025) for refined borates, with units as printed. US imports of all boron forms were 90 percent from Turkey in 2021 to 2024.",
      "producers": [],
      "critical_lists": [
        {
          "list": "USGS 2025 Final List of Critical Minerals (boron added in the 2025 list)",
          "listed": true
        }
      ],
      "recycling": "Not stated in the USGS boron chapter read.",
      "substitutes": [
        "USGS: the substitution of other materials for boron is possible in detergents, enamels, insulation and soaps. This applies to boron in general, not to B4C."
      ],
      "source": "usgs-mcs2026-boron",
      "where": "Events, Trends and Issues (critical minerals paragraph; import sources, All forms 2021 to 2024); World Production and Reserves table; Substitutes"
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "PubChem compound record CID 123279, Boron carbide",
      "type": "database",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/123279"
    },
    {
      "title": "NIST-JANAF Thermochemical Tables, Boron Carbide (B4C), table C-010",
      "type": "database",
      "url": "https://janaf.nist.gov/tables/C-010.html"
    },
    {
      "title": "Saint-Gobain Norbide Hot Pressed Boron Carbide technical data (Form No. B-1050)",
      "type": "datasheet",
      "url": "https://www.ceramicsrefractories.saint-gobain.com/fr/files/3956/view"
    },
    {
      "title": "CoorsTek boron carbide properties table",
      "type": "datasheet",
      "url": "https://coorstek.com/en/materials/boron-carbide/"
    },
    {
      "title": "Stanford Advanced Materials safety data sheet, Boron Carbide, CAS 12069-32-8",
      "type": "sds",
      "url": "https://samaterials.com/tds/1721380172-bc3503.pdf"
    },
    {
      "title": "USGS Mineral Commodity Summaries 2026, Boron",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-boron.pdf"
    },
    {
      "title": "NASA NTRS 20230003044, B4C-Al Metal Matrix Composites for Extreme Space Environments",
      "type": "report",
      "url": "https://ntrs.nasa.gov/citations/20230003044"
    },
    {
      "title": "Varadachari, Bhowmick and Ghosh 2018, Thermodynamics of oxidation and nitridation reactions of boron carbide",
      "type": "paper",
      "url": "https://zenodo.org/records/5642712"
    }
  ],
  "gaps": [
    "NIST Structural Ceramics Database: no boron carbide entry was located. The searches returned SiC and TiB2 entries only, so no NIST B4C mechanical values are used.",
    "Vickers hardness and elastic modulus from Wikipedia (38 GPa and 460 GPa) are not used, because the brief limits Wikipedia to composition and history.",
    "PubChem density (2.5 @25 °C) is not used: the record prints no unit, and the brief forbids inferring one.",
    "PubChem melting point (2350 °C) is not used: the source check cannot match it, because stripping tags from the PubChem JSON removes the Experimental Properties section. The value was read in the record but is left out of the file.",
    "Neutron absorption cross section and boron-10 content: not read in a fetched page. The EPJ Nuclear Sciences 2015 review and the MDPI Materials 2020 review both returned HTTP 403 and were not read.",
    "Ballistic performance and amorphization under high-velocity impact: no fetched source. A search snippet gave an impact threshold near 850 m/s, which is not used.",
    "Ageing under neutron irradiation (helium build-up, swelling, B4C degradation): no source read in this run.",
    "Oxidation onset temperature and rates: the 2018 study gives a temperature range of 273 to 2300 K and no rates. Onset temperatures in search snippets (about 600 and 700 °C) were not read in a fetched page and are not used.",
    "Hazard classifications differ. PubChem gives Danger with H360 and H360FD from 41 of 185 reports (aggregated ECHA notifications). The supplier SDS gives Warning with H332, H315, H319 and H335. Both are recorded; no SDS from a manufacturer was read.",
    "Atomic weights of boron and carbon: not read in a fetched page, so the recipe parts carry no atomic_weight. PubChem gives a computed molecular weight of 55.3, which is not used as a part weight.",
    "Production shares of boron carbide: not found. The USGS boron table prints the world total as XX, so no share is calculated. The USGS 2026 abrasives chapter excerpt returned by search does not name boron carbide, and that chapter was not read in full.",
    "Recycling of boron carbide: not stated in any source read.",
    "Names not in property-canon.yaml: molar_heat_capacity, standard_molar_entropy, standard_enthalpy_of_formation, knoop_hardness, compressive_strength and fracture_toughness. The JANAF values are molar and cannot be converted to the canonical specific_heat unit without a molar mass.",
    "Grades and test methods differ between the Saint-Gobain datasheet (2004, Knoop and indentation toughness) and the CoorsTek table (K Ic and MOR). The two are kept side by side and not merged onto one scale.",
    "Saint-Gobain datasheet is dated 2004 (Form No. B-1050, 11/04). It is the only source here with a full property table.",
    "The 2018 oxidation study and the PubChem record are the only sources for the corrosion section. No manufacturer or NASA source on B4C corrosion was read."
  ],
  "story": {
    "why": "Boron carbide is used where hardness, low density and neutron capture matter. The Saint-Gobain datasheet gives a density of 2.50 gm/cm3 and a Knoop hardness of 2800 kg/mm2 for the hot-pressed grade. NASA's 2023 study credits the boron in B4C for the neutron shielding gain when it is added to aluminium alloy 6061.",
    "uses": [
      {
        "where": "Neutron shielding in aluminium composites",
        "line": "NASA's 2023 Langley study reports that 50 vol percent B4C in Al6061 raised neutron shielding effectiveness more than 110 times over pristine Al6061. The abstract says tensile strength rose up to 20 vol percent."
      },
      {
        "where": "Armor tiles and wear parts",
        "line": "Saint-Gobain lists ballistic armor tiles, blast nozzles and wear-resistant components among the applications of Norbide hot-pressed boron carbide."
      }
    ],
    "can_do": [
      {
        "label": "Hardness",
        "line": "The hot-pressed grade has a Knoop hardness of 2800 kg/mm2 at a 0.1 kg load (Saint-Gobain). Knoop values are not comparable with Vickers values.",
        "benchmark": "knoop_hardness",
        "scope": "material"
      },
      {
        "label": "Stiffness",
        "line": "The hot-pressed grade has an elastic modulus of 440 GPa at room temperature (Saint-Gobain).",
        "benchmark": "elastic_modulus",
        "scope": "material"
      }
    ],
    "compare": "Across the hot-pressed range in CoorsTek's table, flexural strength is 320 to 450 MPa and thermal conductivity is 45 to 100 W/m K at 20 °C. The Saint-Gobain hot-pressed grade's flexural strength (425 MPa) and thermal conductivity (90 W/mK) sit inside those ranges, so the spread reflects grades and test methods rather than one material.",
    "compare_rows": [
      {
        "label": "Flexural strength",
        "benchmark": "flexural_strength",
        "scope": "material"
      },
      {
        "label": "Thermal conductivity",
        "benchmark": "thermal_conductivity",
        "scope": "material"
      },
      {
        "label": "Coefficient of thermal expansion",
        "benchmark": "cte",
        "scope": "material"
      }
    ],
    "handling": [
      "Brittle material. Design for tension and bending loads with a safety margin.",
      "Dust: the SDS lists H332 and H335 and PubChem lists H360. Control dust when grinding or machining, and check the supplier SDS.",
      "Oxidation: the 2018 study says B2O3 forms first and shields the surface in air, but traces of nitrogen can affect quality and hardness."
    ],
    "good_for": [
      "Hard, wear-resistant parts. Saint-Gobain gives a Knoop hardness of 2800 kg/mm2 for the hot-pressed grade.",
      "Neutron shielding in composites. NASA reports a more than 110-fold gain in shielding effectiveness at 50 vol percent B4C in Al6061."
    ],
    "watch_out": [
      "Brittleness. Hot-pressed B4C has a flexural strength of 425 MPa and an indentation fracture toughness of 3.1 MPa x m1/2 (Saint-Gobain).",
      "The hazard classifications disagree. PubChem lists H360 and the supplier SDS lists H332, H315, H319 and H335. Read a manufacturer's SDS before handling.",
      "Neutron-irradiation ageing, Vickers hardness, production shares and armor performance were not sourced in this run."
    ],
    "verdict": "Boron carbide is a very hard, low-density ceramic (2.50 gm/cm3 for the hot-pressed grade). Its datasheet values, its neutron-shielding and armor uses, and its oxidation behaviour are sourced here. Brittleness and the disagreeing hazard classifications need attention. Ageing under neutron irradiation, Vickers hardness and production shares are not yet sourced.",
    "recipe": {
      "line": "Boron carbide is a family of boron-carbon compounds, nominally B4C at the carbon-rich end, with a rhombohedral icosahedron-based structure (Wikipedia). CoorsTek makes it in three forms: reaction bonded, hot pressed and sintered (CoorsTek table). Hot-pressed grades are sold by Saint-Gobain as Norbide (Saint-Gobain datasheet). Henri Moissan first synthesized it (Wikipedia, Preparation).",
      "parts": [
        {
          "name": "Boron",
          "symbol": "B",
          "role": "Makes up most of the compound. NASA's 2023 study credits the boron in B4C for the neutron shielding gain."
        },
        {
          "name": "Carbon",
          "symbol": "C",
          "role": "Forms the icosahedral boron-carbon network with the boron, giving the very high hardness."
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "The two hazard sources disagree on the classification. Treat the material as a dust hazard until a manufacturer's SDS is read.",
        "points": [
          {
            "label": "Dust",
            "line": "Grinding or machining B4C makes fine dust. Control it with extraction and check the supplier's safety data sheet before handling powder or parts."
          },
          {
            "label": "Inhalation",
            "line": "The SDS gives H332 (harmful if inhaled) and H335 (may cause respiratory irritation). PubChem's notifications give H360 and H360FD (reproductive toxicity). 77.8 percent of company reports say the material does not meet GHS criteria."
          }
        ],
        "level": 0,
        "verdict": "PubChem lists H360 (reproductive); SDS lists irritation."
      },
      {
        "title": "If a part fails",
        "lead": "These numbers come from the Saint-Gobain and CoorsTek tables.",
        "points": [
          {
            "label": "Brittleness",
            "line": "Hot-pressed B4C has a four-point flexural strength of 425 MPa (Saint-Gobain), and an indentation fracture toughness of 3.1 MPa x m1/2. It breaks rather than bends under a flaw."
          }
        ]
      }
    ]
  },
  "updated": "2026-10-26",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 16,
    "unreachable": 3,
    "caveats": 4,
    "note": "Written in this run from pages read in this run: the PubChem REST record, the NIST JANAF table, the Saint-Gobain datasheet, the CoorsTek table, the Stanford SDS, the USGS boron chapter 2026, the NASA NTRS abstract, the 2018 Zenodo abstract and Wikipedia for composition and history. The PubChem HTML page showed a browser check, the EPJ 2015 review and the MDPI 2020 review returned HTTP 403, and none of the three was read."
  },
  "sources": {
    "pubchem-b4c": {
      "title": "PubChem compound CID 123279, Boron carbide (experimental properties, GHS classification, uses), read from the PubChem REST record",
      "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/123279/JSON",
      "kind": "database",
      "license": "PubChem public database"
    },
    "janaf-b4c": {
      "title": "NIST-JANAF Thermochemical Tables, Boron Carbide (B4C), table C-010",
      "url": "https://janaf.nist.gov/tables/C-010.html",
      "kind": "database",
      "license": "NIST public data"
    },
    "sg-norbide-hp": {
      "title": "Saint-Gobain Ceramics, Norbide Hot Pressed Boron Carbide Technical Data (Form No. B-1050, 11/04)",
      "url": "https://www.ceramicsrefractories.saint-gobain.com/fr/files/3956/view",
      "kind": "datasheet",
      "license": "vendor datasheet, cited not reproduced"
    },
    "coors-b4c": {
      "title": "CoorsTek, Boron Carbide material properties table (reaction bonded, hot pressed, sintered)",
      "url": "https://coorstek.com/en/materials/boron-carbide/",
      "kind": "web",
      "license": "vendor web page, cited not reproduced"
    },
    "sds-stanford-b4c": {
      "title": "Stanford Advanced Materials, Safety Data Sheet, Boron Carbide (CAS 12069-32-8), revised 10/11/2022",
      "url": "https://samaterials.com/tds/1721380172-bc3503.pdf",
      "kind": "datasheet",
      "license": "vendor safety data sheet, cited not reproduced"
    },
    "usgs-mcs2026-boron": {
      "title": "USGS Mineral Commodity Summaries 2026, Boron",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-boron.pdf",
      "kind": "report",
      "license": "US government work, public domain"
    },
    "ntrs-20230003044": {
      "title": "Chu et al. 2023, B4C-Al Metal Matrix Composites for Extreme Space Environments, NASA NTRS 20230003044",
      "url": "https://ntrs.nasa.gov/citations/20230003044",
      "kind": "report",
      "license": "NASA public document"
    },
    "zenodo-b4c-oxidation": {
      "title": "Varadachari, Bhowmick and Ghosh 2018, Thermodynamics of oxidation and nitridation reactions of boron carbide (Zenodo record 5642712)",
      "url": "https://zenodo.org/records/5642712",
      "kind": "paper",
      "license": "open access record"
    },
    "wikipedia-b4c": {
      "title": "Wikipedia, Boron carbide (composition, history and uses only)",
      "url": "https://en.wikipedia.org/wiki/Boron_carbide",
      "kind": "web",
      "license": "CC-BY-SA 4.0"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/boron-carbide/"
}