{
  "spore": "profile",
  "id": "zirconium-hydride",
  "spore_version": "0.2",
  "family": "zirconium-hydride",
  "name": "Zirconium hydride (ZrH2)",
  "abbreviation": "ZrH2",
  "role": "neutron moderator, getter and hydrogen source",
  "category": "metals",
  "type": "refractory-metals",
  "summary": "Zirconium hydride (ZrH2) is a grey-black powder of zirconium and hydrogen, with two hydrogen atoms for each zirconium atom in the formula. Albemarle's Grade G sets a minimum zirconium-plus-hafnium content of 97.6 % and a minimum hydrogen content of 1.9 %, with a density of 5.6 g/cm3 at 25 °C. The datasheet gives a decomposition temperature above 400 °C and says the material decomposes before it melts. It is a flammable solid with a dust explosion hazard, and PubChem records that it releases flammable gas on contact with water.\n",
  "best_for": "Compact hydrogen storage in a powder: 1.9 % minimum hydrogen content (Albemarle Grade G) with decomposition only above 400 °C",
  "weakest_at": "Fire and water safety: a flammable solid with a dust explosion hazard that can give off flammable gas on contact with water (datasheet and PubChem)",
  "identity": {
    "formula": "ZrH2",
    "cas": "7704-99-6",
    "designations": [
      {
        "system": "Trade name",
        "code": "Zirconium Hydride, Grade G",
        "source": "albemarle-zrh-g",
        "where": "Title of the technical data sheet"
      }
    ],
    "source": "albemarle-zrh-g",
    "where": "Title block of the Albemarle datasheet (CAS-No. 7704-99-6, Molecular formula ZrH2). PubChem CID 4137802 prints the same CAS number."
  },
  "tags": {
    "environments": [],
    "stresses": [],
    "applications": [
      "structures",
      "propulsion-and-tanks",
      "electronics-and-chips"
    ]
  },
  "properties": [
    {
      "benchmark": "density",
      "label": "Density, Grade G at 25 °C",
      "value": 5.6,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "temperature": "25 °C",
        "grade": "Zirconium Hydride, Grade G (product numbers 10000387, 10001973, 10001974)"
      },
      "method": "Value printed in the manufacturer's technical data sheet, which says the value is taken from reference works and the literature rather than a supplier measurement",
      "status": "ground",
      "note": "A reseller page for the same compound prints a density of 5,80 g/cm3 with no conditions. It conflicts with this value and is not recorded as a second property (see gaps).",
      "source": "albemarle-zrh-g",
      "where": "Physical properties table, Density row",
      "source_detail": {
        "title": "Zirconium Hydride, Grade G: technical data sheet",
        "id": "Albemarle, product numbers 10000387, 10001973, 10001974; date of issue 2021/07/22; CAS 7704-99-6; EC 231-727-3",
        "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-g.PDF",
        "year": 2021,
        "kind": "datasheet",
        "license": "manufacturer document, linked not reproduced"
      }
    },
    {
      "benchmark": "decomposition_temperature",
      "label": "Decomposition temperature (decomposes before melting)",
      "value": 400,
      "bound": "lower",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "grade": "Grade G powder",
        "note_in_source": "Decomposes before melting"
      },
      "method": "Printed in the datasheet as > 400 °C; the datasheet gives no melting point",
      "status": "ground",
      "source": "albemarle-zrh-g",
      "where": "Physical properties table, Decomposition temperature row",
      "source_detail": {
        "title": "Zirconium Hydride, Grade G: technical data sheet",
        "id": "Albemarle, product numbers 10000387, 10001973, 10001974; date of issue 2021/07/22; CAS 7704-99-6; EC 231-727-3",
        "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-g.PDF",
        "year": 2021,
        "kind": "datasheet",
        "license": "manufacturer document, linked not reproduced"
      }
    },
    {
      "benchmark": "molecular_weight",
      "label": "Molecular weight",
      "value": 93.24,
      "bound": "exact",
      "unit": "g/mol",
      "scope": "material",
      "conditions": {
        "formula": "ZrH2"
      },
      "method": "Value printed in the manufacturer's technical data sheet",
      "status": "ground",
      "source": "albemarle-zrh-g",
      "where": "Physical properties table, Molecular weight row",
      "source_detail": {
        "title": "Zirconium Hydride, Grade G: technical data sheet",
        "id": "Albemarle, product numbers 10000387, 10001973, 10001974; date of issue 2021/07/22; CAS 7704-99-6; EC 231-727-3",
        "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-g.PDF",
        "year": 2021,
        "kind": "datasheet",
        "license": "manufacturer document, linked not reproduced"
      }
    },
    {
      "benchmark": "zirconium_hafnium_content",
      "label": "Zirconium plus hafnium content (minimum)",
      "value": 97.6,
      "bound": "lower",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "grade": "Grade G",
        "tolerance": "+/- 0.5 % as printed",
        "basis": "Zr + Hf, the datasheet's wording"
      },
      "method": "Specification minimum printed in the manufacturer's datasheet",
      "status": "ground",
      "source": "albemarle-zrh-g",
      "where": "Specification table, row Zr + Hf",
      "source_detail": {
        "title": "Zirconium Hydride, Grade G: technical data sheet",
        "id": "Albemarle, product numbers 10000387, 10001973, 10001974; date of issue 2021/07/22; CAS 7704-99-6; EC 231-727-3",
        "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-g.PDF",
        "year": 2021,
        "kind": "datasheet",
        "license": "manufacturer document, linked not reproduced"
      }
    },
    {
      "benchmark": "hafnium_content",
      "label": "Hafnium content (natural)",
      "value": 2,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "basis": "natural hafnium content, printed as approx. 2 %"
      },
      "method": "Value printed in the manufacturer's datasheet",
      "status": "ground",
      "source": "albemarle-zrh-g",
      "where": "Specification table, row Hf",
      "source_detail": {
        "title": "Zirconium Hydride, Grade G: technical data sheet",
        "id": "Albemarle, product numbers 10000387, 10001973, 10001974; date of issue 2021/07/22; CAS 7704-99-6; EC 231-727-3",
        "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-g.PDF",
        "year": 2021,
        "kind": "datasheet",
        "license": "manufacturer document, linked not reproduced"
      }
    },
    {
      "benchmark": "hydrogen_content",
      "label": "Hydrogen content (minimum)",
      "value": 1.9,
      "bound": "lower",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "basis": "minimum hydrogen content as printed in the specification"
      },
      "method": "Specification minimum printed in the manufacturer's datasheet",
      "status": "ground",
      "source": "albemarle-zrh-g",
      "where": "Specification table, row H",
      "source_detail": {
        "title": "Zirconium Hydride, Grade G: technical data sheet",
        "id": "Albemarle, product numbers 10000387, 10001973, 10001974; date of issue 2021/07/22; CAS 7704-99-6; EC 231-727-3",
        "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-g.PDF",
        "year": 2021,
        "kind": "datasheet",
        "license": "manufacturer document, linked not reproduced"
      }
    },
    {
      "benchmark": "iron_content",
      "label": "Iron impurity (maximum)",
      "value": 0.08,
      "bound": "upper",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "basis": "maximum impurity as printed"
      },
      "method": "Specification maximum printed in the manufacturer's datasheet",
      "status": "ground",
      "source": "albemarle-zrh-g",
      "where": "Specification table, row Fe",
      "source_detail": {
        "title": "Zirconium Hydride, Grade G: technical data sheet",
        "id": "Albemarle, product numbers 10000387, 10001973, 10001974; date of issue 2021/07/22; CAS 7704-99-6; EC 231-727-3",
        "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-g.PDF",
        "year": 2021,
        "kind": "datasheet",
        "license": "manufacturer document, linked not reproduced"
      }
    },
    {
      "benchmark": "silicon_content",
      "label": "Silicon impurity (maximum)",
      "value": 0.5,
      "bound": "upper",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "basis": "maximum impurity as printed"
      },
      "method": "Specification maximum printed in the manufacturer's datasheet",
      "status": "ground",
      "source": "albemarle-zrh-g",
      "where": "Specification table, row Si",
      "source_detail": {
        "title": "Zirconium Hydride, Grade G: technical data sheet",
        "id": "Albemarle, product numbers 10000387, 10001973, 10001974; date of issue 2021/07/22; CAS 7704-99-6; EC 231-727-3",
        "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-g.PDF",
        "year": 2021,
        "kind": "datasheet",
        "license": "manufacturer document, linked not reproduced"
      }
    },
    {
      "benchmark": "ignition_temperature",
      "label": "Ignition point of the powder",
      "value": 200,
      "value_high": 310,
      "bound": "range",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "form": "powder, Grade G"
      },
      "method": "Range printed in the manufacturer's datasheet under Additional Physical Properties",
      "status": "ground",
      "source": "albemarle-zrh-g",
      "where": "Physical properties table, Additional Physical Properties row (Ignition Point)",
      "source_detail": {
        "title": "Zirconium Hydride, Grade G: technical data sheet",
        "id": "Albemarle, product numbers 10000387, 10001973, 10001974; date of issue 2021/07/22; CAS 7704-99-6; EC 231-727-3",
        "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-g.PDF",
        "year": 2021,
        "kind": "datasheet",
        "license": "manufacturer document, linked not reproduced"
      }
    },
    {
      "benchmark": "bulk_density",
      "label": "Bulk density of the powder",
      "value": 1000,
      "value_high": 2000,
      "bound": "range",
      "unit": "kg/m3",
      "scope": "material",
      "conditions": {
        "form": "powder, as printed"
      },
      "method": "Range printed in the manufacturer's datasheet",
      "status": "ground",
      "source": "albemarle-zrh-g",
      "where": "Physical properties table, Bulk density row",
      "source_detail": {
        "title": "Zirconium Hydride, Grade G: technical data sheet",
        "id": "Albemarle, product numbers 10000387, 10001973, 10001974; date of issue 2021/07/22; CAS 7704-99-6; EC 231-727-3",
        "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-g.PDF",
        "year": 2021,
        "kind": "datasheet",
        "license": "manufacturer document, linked not reproduced"
      }
    },
    {
      "benchmark": "water_solubility",
      "label": "Water solubility",
      "value": 0.00008,
      "bound": "upper",
      "unit": "g/l",
      "scope": "material",
      "conditions": {
        "temperature": "23 °C",
        "test": "OECD Test Guideline 29, as printed"
      },
      "method": "Printed in the datasheet as < 0.00008 g/l at 23 °C",
      "status": "ground",
      "source": "albemarle-zrh-g",
      "where": "Physical properties table, Water solubility row",
      "source_detail": {
        "title": "Zirconium Hydride, Grade G: technical data sheet",
        "id": "Albemarle, product numbers 10000387, 10001973, 10001974; date of issue 2021/07/22; CAS 7704-99-6; EC 231-727-3",
        "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-g.PDF",
        "year": 2021,
        "kind": "datasheet",
        "license": "manufacturer document, linked not reproduced"
      }
    },
    {
      "benchmark": "average_particle_size",
      "label": "Average particle size (Blaine)",
      "value": 5.5,
      "bound": "exact",
      "unit": "µm",
      "scope": "material",
      "conditions": {
        "method_printed": "Blaine",
        "tolerance": "+/- 1 µm as printed"
      },
      "method": "Printed in the datasheet as average particle size acc. to Blaine",
      "status": "ground",
      "source": "albemarle-zrh-g",
      "where": "Physical properties table, Grain Size row",
      "source_detail": {
        "title": "Zirconium Hydride, Grade G: technical data sheet",
        "id": "Albemarle, product numbers 10000387, 10001973, 10001974; date of issue 2021/07/22; CAS 7704-99-6; EC 231-727-3",
        "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-g.PDF",
        "year": 2021,
        "kind": "datasheet",
        "license": "manufacturer document, linked not reproduced"
      }
    },
    {
      "benchmark": "particle_size_under_45um",
      "label": "Share of powder finer than 45 µm (minimum)",
      "value": 99.9,
      "bound": "lower",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "size_limit": "below 45 µm"
      },
      "method": "Printed in the datasheet as min. 99.9 % < 45 µm",
      "status": "ground",
      "source": "albemarle-zrh-g",
      "where": "Physical properties table, Grain Size row",
      "source_detail": {
        "title": "Zirconium Hydride, Grade G: technical data sheet",
        "id": "Albemarle, product numbers 10000387, 10001973, 10001974; date of issue 2021/07/22; CAS 7704-99-6; EC 231-727-3",
        "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-g.PDF",
        "year": 2021,
        "kind": "datasheet",
        "license": "manufacturer document, linked not reproduced"
      }
    },
    {
      "benchmark": "gain_on_ignition",
      "label": "Weight gain on combustion",
      "value": 31.8,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "basis": "weight increase by combustion, as the datasheet defines it",
        "tolerance": "+/- 0.7 % as printed"
      },
      "method": "Printed in the datasheet under Additional Physical Properties",
      "status": "ground",
      "source": "albemarle-zrh-g",
      "where": "Physical properties table, Additional Physical Properties row (Gain on Ignition)",
      "source_detail": {
        "title": "Zirconium Hydride, Grade G: technical data sheet",
        "id": "Albemarle, product numbers 10000387, 10001973, 10001974; date of issue 2021/07/22; CAS 7704-99-6; EC 231-727-3",
        "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-g.PDF",
        "year": 2021,
        "kind": "datasheet",
        "license": "manufacturer document, linked not reproduced"
      }
    },
    {
      "benchmark": "relative_density",
      "label": "Relative density of cold-pressed disks",
      "value": 73,
      "bound": "exact",
      "unit": "% of theoretical density",
      "scope": "material",
      "conditions": {
        "form": "cold-pressed disk of zirconium hydride (ZrHx) powder, commercial 99 % purity, 50 mesh",
        "pressure": "400 MPa"
      },
      "method": "Density calculated by the authors from the weight and dimensions of the pressed disk",
      "status": "ground",
      "note": "A pressed compact from a research study, not a bulk value for this grade. The same report gives thermal conductivity only as a figure, so no thermal value is recorded.",
      "source": "nifs-zrhx-pressed",
      "where": "Text, paragraph beginning 'Sample with 73 % of theoretical density'",
      "source_detail": {
        "title": "Applicability Study of Hydride Materials (section 41), NIFS Annual Report 2013",
        "id": "NIFS annual report 2013, p. 360",
        "url": "https://www.nifs.ac.jp/report/annrep13/pdf/360.pdf",
        "year": 2013,
        "kind": "report",
        "license": "NIFS report, cited not reproduced"
      }
    },
    {
      "benchmark": "purity",
      "label": "Stated purity of a micron powder",
      "value": 99.5,
      "bound": "lower",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "grade": "micron powder, size printed as 1-10 µm on the reseller page",
        "definition": "not defined on the page"
      },
      "method": "Stated in the product title and specification table of a reseller's product page",
      "status": "ground",
      "note": "The reseller does not define its purity figure. The datasheet's Zr + Hf minimum of 97.6 % is defined differently, so the two are not directly comparable.",
      "source": "nanografi-zrh",
      "where": "Product title ('Purity: 99.5+%') and specification table, Purity row",
      "source_detail": {
        "title": "Zirconium Hydride (ZrH2) Micron Powder, Purity 99.5+% (reseller product page)",
        "id": "Nanografi SKU NG04CO2801",
        "url": "https://shop.nanografi.com/microparticles/zirconium-hydride-zrh2-micron-powder-purity-99-5-size-1-10-m/",
        "year": 2026,
        "kind": "web",
        "license": "reseller page, cited not reproduced"
      }
    }
  ],
  "corrosion": [
    {
      "environment": "Water, or humid air",
      "headline": "Sources disagree on whether zirconium hydride reacts with water. Both say that any gas released is flammable.",
      "effect": "PubChem's record description says the powder does not react with water under normal conditions. Its hazards summary says the powder reacts slowly with water to form zirconium hydroxide and hydrogen gas, which is flammable, and another entry says it releases flammable gases on contact with water.",
      "rating": "moderate",
      "conditions": {
        "water": "temperature and exposure time not stated",
        "form": "powder"
      },
      "source": "pubchem-zrh",
      "where": "Chemical and Physical Properties, Physical Description; Safety and Hazards, Hazards Summary; Stability and Reactivity, Air and Water Reactions"
    },
    {
      "environment": "Heating in air",
      "headline": "Heated in air, the powder incandesces and can give mild explosions.",
      "effect": "PubChem cites Bretherick (1979) for heating in air causing incandescence and mild explosions. The datasheet gives an ignition point of 200 to 310 °C and a gain of 31.8 % in weight on combustion.",
      "rating": "moderate",
      "conditions": {
        "basis": "heating in air, no exposure time stated"
      },
      "source": "pubchem-zrh",
      "where": "Stability and Reactivity, Air and Water Reactions"
    },
    {
      "environment": "Dry, sealed storage",
      "headline": "The datasheet gives an unlimited shelf life for dry, sealed storage.",
      "effect": "Albemarle states an unlimited shelf life and packs the powder dry in tin cans. It gives no ageing data, such as change in hydrogen content over time.",
      "rating": "none",
      "conditions": {
        "packaging": "dry, in sealed tin cans",
        "condition": "dry storage"
      },
      "source": "albemarle-zrh-g",
      "where": "Handling and Storage; Transport and Packaging"
    }
  ],
  "risks": {
    "hazards": [
      {
        "text": "PubChem's GHS summary: signal word Danger. Hazard statements H228 (flammable solid), H260 (in contact with water releases flammable gases which may ignite spontaneously), H315 (causes skin irritation) and H319 (causes serious eye irritation). Percentages are shares of ECHA notifications, not of tests.",
        "ghs": [
          "H228",
          "H260",
          "H315",
          "H319"
        ],
        "source": "pubchem-zrh",
        "where": "Safety and Hazards, GHS Classification (CID 4137802)"
      },
      {
        "text": "Albemarle datasheet: signal word Danger and EU-GHS labelling. Transport: UN 1437, Class 4.1 flammable solid, Packing Group II for road, rail and sea, and Packing Group II for air.",
        "ghs": [],
        "source": "albemarle-zrh-g",
        "where": "Transport and Packaging; Labelling"
      },
      {
        "text": "Exposure limits in PubChem (5.0 mg/m3 as Zr, the PEL and TLV, and 10.0 mg/m3 as Zr for the STEL) are for zirconium compounds in general, not for zirconium hydride alone.",
        "ghs": [],
        "source": "pubchem-zrh",
        "where": "Exposure Control and Personal Protection, PEL and TLV entries"
      }
    ],
    "failure_risks": [
      {
        "mode": "Dust ignition",
        "trigger": "Powder dust formed during handling or transfer, or an open flame or spark nearby",
        "consequence": "The datasheet calls the powder a highly flammable solid with a dust explosion hazard. It gives an ignition point of 200 to 310 °C and says the powder is less ignitable than other grades because of its coarse particle size.",
        "severity": "high",
        "source": "albemarle-zrh-g",
        "where": "Handling and Storage; Physical properties table, Ignition Point"
      },
      {
        "mode": "Reaction with water",
        "trigger": "Contact with water, including water sprayed on a fire",
        "consequence": "Flammable hydrogen gas is released. PubChem's GHS statement H260 says contact with water releases flammable gases which may ignite spontaneously, and the ERG notes say the product may re-ignite after a fire is put out.",
        "severity": "high",
        "source": "pubchem-zrh",
        "where": "GHS Classification (H260); Fire Hazards, ERG 2024 Guide 138"
      },
      {
        "mode": "Hydrogen loss on heating",
        "trigger": "Heating above the decomposition temperature",
        "consequence": "The datasheet reports decomposition above 400 °C, not melting. It does not state how much hydrogen is released or how the lost hydrogen affects the material's behaviour.",
        "severity": "moderate",
        "source": "albemarle-zrh-g",
        "where": "Physical properties table, Decomposition temperature row"
      }
    ],
    "side_effects": [
      {
        "text": "Fire produces irritating, corrosive and/or toxic gases (ERG 2024, Guide 138).",
        "affects": "Responders and nearby people",
        "source": "pubchem-zrh",
        "where": "Safety and Hazards, Health Hazards (ERG 2024 Guide 138)"
      },
      {
        "text": "Runoff from fire control or dilution water may cause environmental contamination (ERG 2024, Guide 138).",
        "affects": "Waterways near the site",
        "source": "pubchem-zrh",
        "where": "Safety and Hazards, Health Hazards (ERG 2024 Guide 138)"
      }
    ],
    "handling": [
      {
        "text": "Datasheet: highly flammable solid with a dust explosion hazard. Keep away from open flame and use ground-connected metal apparatus to avoid sudden ignition by electrostatic discharge.",
        "source": "albemarle-zrh-g",
        "where": "Handling and Storage"
      },
      {
        "text": "Datasheet: store dry in tightly closed tin cans. The datasheet says the product has an unlimited shelf life.",
        "source": "albemarle-zrh-g",
        "where": "Handling and Storage; Packaging"
      },
      {
        "text": "PubChem's ERG 2024 Guide 138 notes: eliminate ignition sources and cover powder spills with plastic sheet to keep the powder dry; do not clean up powder except under specialist supervision.",
        "source": "pubchem-zrh",
        "where": "Accidental Release Measures; Nonfire Spill Response"
      }
    ],
    "mitigations": [
      {
        "text": "Fight fires with dry sand or dry powder only, and never with water. PubChem's ERG notes say do not use water or foam.",
        "source": "pubchem-zrh",
        "where": "Fire Fighting; Emergency Response Planning Guidelines (ERG 2024 Guide 138)"
      },
      {
        "text": "Use ground-connected metallic equipment to prevent sudden ignition by electrostatic discharge.",
        "source": "albemarle-zrh-g",
        "where": "Handling and Storage"
      }
    ]
  },
  "uses": [
    {
      "application": "structures",
      "device": "Hydrogen source for foaming metals",
      "example": "The datasheet names zirconium hydride as a hydrogen source for the foaming of metals. PubChem also lists its use as a metal foaming agent.",
      "source": "albemarle-zrh-g",
      "where": "Application paragraph; PubChem Uses, Sources/Uses entry"
    },
    {
      "application": "propulsion-and-tanks",
      "device": "Moderator block in a nuclear thermal propulsion reactor (conceptual reference design, not flown)",
      "example": "A 2021 NETS paper on NASA's space nuclear propulsion fuel and moderator plan says the Heat Transfer Reactor Experiment used solid zirconium-hydride moderator blocks, and it recommends a ZrH moderator block for the reference core it describes.",
      "source": "nets-snp-fmdp",
      "where": "Section I, paragraph on moderator material selection (HTRE reference)"
    },
    {
      "application": "electronics-and-chips",
      "device": "Getter material (the device is not named in the datasheet)",
      "example": "The datasheet says the grade is for the production of highly effective getters, which are activated by dehydrogenation.",
      "source": "albemarle-zrh-g",
      "where": "Application paragraph"
    }
  ],
  "supply": [
    {
      "subject": "Zirconium (from zircon and zirconium mineral concentrates)",
      "producers": [
        {
          "country": "Australia",
          "share_percent": 33.3,
          "year": 2025
        },
        {
          "country": "South Africa",
          "share_percent": 22.5,
          "year": 2025
        },
        {
          "country": "Mozambique",
          "share_percent": 13.3,
          "year": 2025
        },
        {
          "country": "China",
          "share_percent": 8.3,
          "year": 2025
        }
      ],
      "critical_lists": [],
      "recycling": "USGS: companies in Oregon and Utah recycled zirconium from new scrap and post-commercial old scrap.",
      "substitutes": [
        "USGS: niobium, stainless steel and tantalum provide some substitution in nuclear applications. The chapter covers zirconium and hafnium together."
      ],
      "source": "usgs-mcs2026-zirconium-hafnium",
      "where": "World Mine Production and Reserves table, zirconium mineral concentrates, 2025 (thousand metric tons gross weight: Australia 400, South Africa 270, Mozambique 160, China 100, against a world total of 1,200). Shares are calculated by Space Mushroom against that rounded total, so they are approximate. Recycling and Substitutes sections."
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "Zirconium Hydride, Grade G: technical data sheet (Albemarle, date of issue 2021/07/22)",
      "type": "datasheet",
      "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-g.PDF",
      "year": 2021
    },
    {
      "title": "PubChem: Zirconium hydride (CID 4137802), GHS classification and safety summaries",
      "type": "database",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/4137802",
      "year": 2026
    },
    {
      "title": "Mineral Commodity Summaries 2026: Zirconium and Hafnium (USGS, February 2026)",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-zirconium-hafnium.pdf",
      "year": 2026
    },
    {
      "title": "Applicability Study of Hydride Materials, NIFS Annual Report 2013, section 41, p. 360",
      "type": "report",
      "url": "https://www.nifs.ac.jp/report/annrep13/pdf/360.pdf",
      "year": 2013
    },
    {
      "title": "High-Temperature Thermodynamic Functions for Zirconium and Unsaturated Zirconium Hydrides (J. Res. NBS 67A, 1963)",
      "type": "paper",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC5319804/",
      "year": 1963
    },
    {
      "title": "Space Nuclear Propulsion Fuel and Moderator Development Plan: Conceptual Testing Reference Design (NETS 2021)",
      "type": "report",
      "url": "https://ntrs.nasa.gov/api/citations/20220000493/downloads/SNP%20FMDP%20Conceptual%20Testing%20Reference%20Design_NETS.pdf",
      "year": 2021
    },
    {
      "title": "TRIGA Type U-ZrH Cladding Steady State Mechanical Limitations (Sandia National Laboratories slides, SAND2009-7374C)",
      "type": "report",
      "url": "https://www.trtr.org/wp-content/uploads/2024/12/TRIGA-Type-U-ZrH-Cladding-Steady-State-Mechanical-Limitations.pdf",
      "year": 2009
    },
    {
      "title": "Zirconium Hydride (ZrH2) Micron Powder, Purity 99.5+% (Nanografi product page)",
      "type": "datasheet",
      "url": "https://shop.nanografi.com/microparticles/zirconium-hydride-zrh2-micron-powder-purity-99-5-size-1-10-m/",
      "year": 2026
    },
    {
      "title": "Atomic Weights and Isotopic Compositions for All Elements (NIST), entry for Zr",
      "type": "database",
      "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=Zr&all=all",
      "year": 2026
    }
  ],
  "gaps": [
    "No melting point for this grade: the datasheet says the material decomposes before melting and gives no melting temperature. A reseller page prints a melting point of 800 °C with no conditions, which conflicts with the datasheet, so it is not recorded.",
    "The reseller page also prints a density of 5,80 g/cm3 with no conditions. It conflicts with the datasheet's 5.6 g/cm3 at 25 °C, so only the datasheet value is recorded.",
    "No thermal conductivity, thermal expansion, elastic modulus or hydrogen equilibrium pressure for pure ZrH2 was read in a fetched source. The NIFS thermal conductivity is shown only as a figure, and the 1963 Douglas paper's thermodynamic tables were not extracted.",
    "The NIFS report's bulk-sample comparison (about 80 W/(m·K)) is a literature figure for a bulk sample, not for this grade, so it is not recorded.",
    "The datasheet gives the decomposition temperature only. It does not state how much hydrogen is released on decomposition.",
    "No flight, vacuum, radiation or space-environment test result for zirconium hydride was found. The NETS paper is a conceptual reference design, not a test result.",
    "The Sandia slide values (density, elastic modulus, thermal expansion) are for uranium-zirconium hydride (U-ZrH) TRIGA fuel, not pure ZrH2, so they are not recorded as properties.",
    "The manufacturing route for the powder was not found in the sources read.",
    "The atomic weight of hydrogen is printed by NIST as an interval rather than a single standard value, so none is recorded in the recipe.",
    "No UNS, EN, ASTM, AMS or other standard designation was found for this grade. Only the trade name Zirconium Hydride, Grade G is listed.",
    "The USGS 2025 critical-minerals list and the EU critical raw materials list were not checked for zirconium, so the supply section names no critical-list entry.",
    "The PubChem exposure limits (5.0 mg/m3 as Zr) apply to zirconium compounds in general and are not limits set for ZrH2 itself.",
    "The fire, water and corrosion hazards rest on PubChem's summaries and the Albemarle datasheet. No supplier safety data sheet for ZrH2 was read."
  ],
  "story": {
    "why": "Zirconium hydride (ZrH2) is a grey-black zirconium powder with a high hydrogen content, sold for three jobs: as a hydrogen source for foaming metals, as a getter that is activated by dehydrogenation, and for illumination effects in pyrotechnics. Its hydrogen makes it a useful neutron moderator. In a 1963 review of the zirconium-hydrogen system, Douglas described zirconium hydrides as potentially valuable thermal neutron moderators that can reach high temperatures without excessive pressure. The datasheet does not name a space application, so the space use here comes from a NASA-sponsored reference design study.",
    "uses": [
      {
        "where": "Metal foaming",
        "line": "The datasheet names zirconium hydride as a hydrogen source for the foaming of metals. PubChem also lists its use as a metal foaming agent."
      },
      {
        "where": "Space nuclear propulsion",
        "line": "A 2021 NETS paper on NASA's space nuclear propulsion fuel and moderator plan says the Heat Transfer Reactor Experiment used solid zirconium-hydride moderator blocks. The paper recommends a ZrH moderator block for the reference core it describes. This is a conceptual reference design, not a flown system."
      },
      {
        "where": "Getters and pyrotechnics",
        "line": "Albemarle makes this grade for highly effective getters, which are activated by dehydrogenation, and for illumination effects in pyrotechnics."
      },
      {
        "where": "Research reactor fuel (a different material)",
        "line": "TRIGA research-reactor fuel uses a uranium-zirconium hydride (U-ZrH) matrix that combines fuel and moderator. A Sandia slide set describes it. That matrix is a different material from pure ZrH2, so its figures are not used in this profile."
      }
    ],
    "can_do": [
      {
        "label": "Hydrogen foaming",
        "line": "Supplies hydrogen for foaming metals, the datasheet's stated application.",
        "scope": "material"
      },
      {
        "label": "Getter",
        "line": "Works as a getter material once it is activated by dehydrogenation, as the datasheet describes.",
        "scope": "material"
      },
      {
        "label": "Moderation",
        "line": "Moderates neutrons in a reactor core. Douglas (1963) calls zirconium hydrides potentially valuable thermal neutron moderators, and the 2021 NETS paper recommends a ZrH moderator block for a space nuclear propulsion core.",
        "scope": "material"
      }
    ],
    "compare": "Two zirconium dihydride powders are on sale from the sources we read. Albemarle's Grade G gives a minimum zirconium-plus-hafnium content of 97.6 % and a minimum hydrogen content of 1.9 %, and it decomposes above 400 °C before melting. Nanografi's micron powder is stated as 99.5+% purity, but its page does not define that figure, so it cannot be set against the Albemarle minimum. Nanografi also prints a melting point with no conditions, which conflicts with the datasheet, and that figure is not used here.",
    "compare_rows": [
      {
        "label": "Density",
        "benchmark": "density",
        "scope": "material"
      },
      {
        "label": "Decomposition temperature",
        "benchmark": "decomposition_temperature",
        "scope": "material"
      },
      {
        "label": "Ignition point",
        "benchmark": "ignition_temperature",
        "scope": "material"
      }
    ],
    "handling": [
      "Keep the powder dry and tightly closed. The datasheet says it has an unlimited shelf life under those conditions.",
      "Keep it away from open flame and sparks. Use ground-connected metal equipment because of the risk of ignition by static discharge.",
      "Put out fires with dry sand or dry powder only, never water. PubChem's ERG notes say do not use water or foam.",
      "Cover powder spills with plastic sheet to keep them dry, and leave cleanup to specialists."
    ],
    "good_for": [
      "Hydrogen delivery in a powder: the datasheet sets a minimum hydrogen content of 1.9 %, which is released only above the decomposition temperature of 400 °C.",
      "Hydrogen-rich moderation in reactor designs, as Douglas (1963) noted and as the 2021 NETS reference design uses it."
    ],
    "watch_out": [
      "A flammable solid with a dust explosion hazard. The datasheet gives an ignition point of 200 to 310 °C.",
      "Water releases flammable gas. PubChem's GHS statement H260 says contact with water releases flammable gases which may ignite spontaneously.",
      "No melting point, thermal conductivity or elastic modulus for this grade was found in any source we read. The NIFS pressed-disk density of 73 % of theoretical is a research compact, not a bulk value."
    ],
    "verdict": "Zirconium hydride is a fire-risk powder that stores hydrogen. It suits foaming, getter and reactor-moderator uses only with fire and water controls in place, and the thermal data a designer would need are not in the sources we hold.",
    "recipe": {
      "line": "Zirconium hydride is the compound ZrH2, zirconium dihydride: one zirconium atom bonded to two hydrogen atoms. The Albemarle datasheet's Grade G is a commercial powder with a minimum zirconium-plus-hafnium content of 97.6 % and a minimum hydrogen content of 1.9 %.",
      "parts": [
        {
          "name": "Zirconium",
          "symbol": "Zr",
          "role": "The metal framework. NIST prints a standard atomic weight of 91.224 for zirconium.",
          "atoms": 1,
          "atomic_weight": 91.224
        },
        {
          "name": "Hydrogen",
          "symbol": "H",
          "role": "Stored inside the metal lattice. It is the part that gives the material its moderating, getter and foaming uses, and it is lost when the material decomposes above 400 °C."
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "The powder is a flammable solid under GHS, and it is an irritant. The hazard data come from a chemical database and from the manufacturer's datasheet.",
        "points": [
          {
            "label": "The powder",
            "line": "PubChem's GHS summary gives H228 (flammable solid), H315 (skin irritation) and H319 (serious eye irritation), with the signal word Danger."
          },
          {
            "label": "Dust",
            "line": "The datasheet warns of a dust explosion hazard. It gives an ignition point of 200 to 310 °C for the powder."
          },
          {
            "label": "Water",
            "line": "PubChem reports that the compound reacts slowly with water to form zirconium hydroxide and hydrogen gas, which is flammable. Another PubChem entry says it does not react with water under normal conditions. The two statements disagree."
          }
        ],
        "verdict": "Flammable solid; irritant; reacts with water"
      },
      {
        "title": "In a fire",
        "lead": "The fire guidance comes from the ERG 2024 entry for this compound, which PubChem reproduces.",
        "points": [
          {
            "label": "What to use",
            "line": "Use dry sand, dry chemical, soda ash or lime. PubChem's ERG notes say do not use water or foam."
          },
          {
            "label": "Fire products",
            "line": "Fire gives off irritating, corrosive and/or toxic gases, and runoff can contaminate the environment."
          }
        ],
        "verdict": "Fire fighting: dry sand or powder only, never water"
      },
      {
        "title": "Handling and storage",
        "points": [
          {
            "label": "Storage",
            "line": "The datasheet says to store the powder dry in tightly closed containers. It gives the product an unlimited shelf life under those conditions."
          },
          {
            "label": "Static",
            "line": "Use ground-connected metal equipment. The datasheet warns of sudden ignition from electrostatic discharge."
          },
          {
            "label": "Transport",
            "line": "Shipped as UN 1437, Class 4.1, flammable solid, Packing Group II."
          }
        ],
        "verdict": "Keep dry and sealed; ground all equipment"
      }
    ]
  },
  "updated": "2026-11-01",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 16,
    "unreachable": 0,
    "caveats": 3,
    "note": "Written by an AI assistant on 2026-11-01 from pages fetched in that run. Values are as printed in the cited sources. The reseller density and melting point conflict with the datasheet and are left out (see gaps)."
  },
  "sources": {
    "albemarle-zrh-g": {
      "title": "Zirconium Hydride, Grade G: technical data sheet",
      "id": "Albemarle, product numbers 10000387, 10001973, 10001974; date of issue 2021/07/22; CAS 7704-99-6; EC 231-727-3",
      "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-g.PDF",
      "year": 2021,
      "kind": "datasheet",
      "license": "manufacturer document, linked not reproduced"
    },
    "pubchem-zrh": {
      "title": "PubChem compound record, Zirconium hydride (CID 4137802)",
      "id": "CID 4137802; CAS 7704-99-6; UN 1437",
      "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/4137802/JSON",
      "year": 2026,
      "kind": "database",
      "license": "public domain (NCBI)"
    },
    "usgs-mcs2026-zirconium-hafnium": {
      "title": "Mineral Commodity Summaries 2026: Zirconium and Hafnium",
      "id": "USGS MCS 2026, February 2026",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-zirconium-hafnium.pdf",
      "year": 2026,
      "kind": "report",
      "license": "public domain (USGS)"
    },
    "nifs-zrhx-pressed": {
      "title": "Applicability Study of Hydride Materials (section 41), NIFS Annual Report 2013",
      "id": "NIFS annual report 2013, p. 360",
      "url": "https://www.nifs.ac.jp/report/annrep13/pdf/360.pdf",
      "year": 2013,
      "kind": "report",
      "license": "NIFS report, cited not reproduced"
    },
    "douglas1963": {
      "title": "High-Temperature Thermodynamic Functions for Zirconium and Unsaturated Zirconium Hydrides",
      "id": "J. Res. Natl. Bur. Stand. A 67A(5), 403-426 (1963); doi:10.6028/jres.067A.043; PMC5319804",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC5319804/",
      "year": 1963,
      "kind": "paper",
      "license": "public domain (NBS/NIST publication, as hosted by PMC)"
    },
    "nets-snp-fmdp": {
      "title": "Space Nuclear Propulsion Fuel and Moderator Development Plan: Conceptual Testing Reference Design",
      "id": "NETS 2021 (ORNL, April 2021), NTRS 20220000493",
      "url": "https://ntrs.nasa.gov/api/citations/20220000493/downloads/SNP%20FMDP%20Conceptual%20Testing%20Reference%20Design_NETS.pdf",
      "year": 2021,
      "kind": "report",
      "license": "public domain (NASA)"
    },
    "sandia-trga-uzrh": {
      "title": "TRIGA Type U-ZrH Cladding Steady State Mechanical Limitations (slides)",
      "id": "Sandia National Laboratories, SAND2009-7374C",
      "url": "https://www.trtr.org/wp-content/uploads/2024/12/TRIGA-Type-U-ZrH-Cladding-Steady-State-Mechanical-Limitations.pdf",
      "year": 2009,
      "kind": "report",
      "license": "slides, cited not reproduced"
    },
    "nanografi-zrh": {
      "title": "Zirconium Hydride (ZrH2) Micron Powder, Purity 99.5+% (reseller product page)",
      "id": "Nanografi SKU NG04CO2801",
      "url": "https://shop.nanografi.com/microparticles/zirconium-hydride-zrh2-micron-powder-purity-99-5-size-1-10-m/",
      "year": 2026,
      "kind": "web",
      "license": "reseller page, cited not reproduced"
    },
    "nist-atomic-weights": {
      "title": "Atomic Weights and Isotopic Compositions for All Elements",
      "id": "NIST Physical Measurement Laboratory, entry for Zr (standard atomic weight 91.224)",
      "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=Zr&all=all",
      "year": 2026,
      "kind": "database",
      "license": "public domain (NIST)"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/zirconium-hydride/"
}