{
  "spore": "profile",
  "id": "titanium-hydride",
  "spore_version": "0.2",
  "family": "refractory-metals",
  "name": "Titanium hydride",
  "abbreviation": "TiH2",
  "role": "hydrogen reservoir, foaming agent and neutron moderator (titanium, zirconium and hafnium hydrides)",
  "category": "metals",
  "type": "refractory-metals",
  "summary": "This profile covers three metal dihydrides that share one powder form and one behaviour: titanium hydride (TiH2), zirconium hydride (ZrH2) and hafnium hydride (HfH2). Albemarle grade N gives TiH2 a density of 3.91 g/cm3 at 20 °C, and its data sheet describes it as a reservoir for pure hydrogen and as a hydrogen source for foaming metals. Hydrogen comes out of the powder on heating: a KTU paper gives 763 K as the release temperature for untreated TiH2. ZrH2 was used as a moderator in the SNAP reactor program, and an INL and Los Alamos review gives a dissociation pressure of 30 atm at 800 °C for the epsilon phase of ZrH1.85. HfH2 powder releases hydrogen in three steps near 350, 415 and 700 °C (Bangor University).\n",
  "best_for": "Hydrogen reservoirs and foaming agents for metal powder processing (Albemarle grade N and the KTU aluminium foam paper), and zirconium hydride as a moderator with a high moderating ratio (ORNL Table 1)",
  "weakest_at": "Hydrogen loss on heating: TiH2 releases hydrogen from about 763 K, ZrH2 evolves hydrogen above 300 °C (ATI), and all three powders are flammable with a dust-explosion risk",
  "identity": {
    "formula": "TiH2 (titanium dihydride), ZrH2 (zirconium dihydride) and HfH2 (hafnium dihydride). Albemarle lists the molecular formula TiH2 for grade N and ZrH2 for grade PS. The Bangor paper writes the hafnium phase as HfH2-x, and the INL review writes zirconium hydride phases as ZrH1.6 and ZrH1.85",
    "cas": "7704-98-5",
    "designations": [],
    "source": "albemarle-tih2-n",
    "where": "Title block, CAS-No. row (TiH2, grade N). CAS 7704-99-6 for ZrH2 (grade PS, Albemarle) and 12770-26-2 for HfH2 (Albemarle product page, metadata)"
  },
  "tags": {
    "environments": [],
    "stresses": [
      "extreme-heat"
    ],
    "applications": [
      "propulsion-and-tanks",
      "radiation-shielding",
      "structures"
    ]
  },
  "properties": [
    {
      "benchmark": "density",
      "label": "Density, TiH2 powder, 20 °C",
      "value": 3.91,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "temperature": "20 °C",
        "form": "powder, grade N"
      },
      "method": "Density printed in the Albemarle grade N technical data sheet, method OPPTS 830.7300",
      "status": "ground",
      "source": "albemarle-tih2-n",
      "where": "Physical and chemical properties table, Density row",
      "source_detail": {
        "title": "Albemarle, Titanium Hydride, Grade N, technical data sheet (issue 2021-07-22)",
        "url": "https://www.albemarle.com/sites/default/files/2025-10/titanium-hydride-grade-n.PDF",
        "year": 2021,
        "kind": "datasheet",
        "license": "supplier technical data sheet, cited not reproduced"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, TiH2, 25 °C (supplier SDS)",
      "value": 3.91,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "temperature": "25 °C (77 °F)"
      },
      "method": "Relative density printed in the Sigma-Aldrich SDS, physical and chemical properties section",
      "status": "ground",
      "source": "sigma-tih2",
      "where": "Physical and chemical properties, item m, Relative density",
      "source_detail": {
        "title": "Sigma-Aldrich, Safety data sheet for titanium hydride (archived copy hosted by Purdue University)",
        "url": "https://www.physics.purdue.edu/primelab/safety/MSDS/SDS/titanium%20hydride%20%20-%20Aldrich.pdf",
        "kind": "datasheet",
        "license": "supplier safety data sheet, cited not reproduced"
      }
    },
    {
      "benchmark": "density",
      "label": "Hydride density, TiH2, ORNL Table 1",
      "value": 3.78,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "basis": "hydride density as tabulated by ORNL, which cites a reference for the table"
      },
      "method": "Printed in the ORNL Table 1 column Hydride density (g/cm3). It differs from the 3.91 g/cm3 manufacturer values and is kept as printed",
      "status": "ground",
      "source": "ornl-zrh-2020",
      "where": "Table 1, TiH2 row, Hydride density column",
      "source_detail": {
        "title": "Hu et al., ORNL/SPR-2020/1672, Fabrication of Zirconium Hydride with Controlled Hydrogen Loading (Oak Ridge National Laboratory)",
        "url": "https://info.ornl.gov/sites/publications/Files/Pub146553.pdf",
        "kind": "report",
        "license": "US Department of Energy report"
      }
    },
    {
      "benchmark": "molar_mass",
      "label": "Molar mass, TiH2",
      "value": 49.88,
      "bound": "exact",
      "unit": "g/mol",
      "scope": "material",
      "conditions": {
        "basis": "molecular weight printed in the supplier SDS, formula H2Ti"
      },
      "method": "Molecular weight printed in the Sigma-Aldrich SDS",
      "status": "ground",
      "source": "sigma-tih2",
      "where": "Composition or ingredients section, Molecular Weight row",
      "source_detail": {
        "title": "Sigma-Aldrich, Safety data sheet for titanium hydride (archived copy hosted by Purdue University)",
        "url": "https://www.physics.purdue.edu/primelab/safety/MSDS/SDS/titanium%20hydride%20%20-%20Aldrich.pdf",
        "kind": "datasheet",
        "license": "supplier safety data sheet, cited not reproduced"
      }
    },
    {
      "benchmark": "hydrogen_content",
      "label": "Hydrogen content, TiH2 grade N, minimum",
      "value": 3.8,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "grade": "N",
        "bound": "minimum"
      },
      "method": "Specification minimum printed in the Albemarle grade N data sheet",
      "status": "ground",
      "source": "albemarle-tih2-n",
      "where": "Specification table, Hydrogen row",
      "source_detail": {
        "title": "Albemarle, Titanium Hydride, Grade N, technical data sheet (issue 2021-07-22)",
        "url": "https://www.albemarle.com/sites/default/files/2025-10/titanium-hydride-grade-n.PDF",
        "year": 2021,
        "kind": "datasheet",
        "license": "supplier technical data sheet, cited not reproduced"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point range, TiH2 (decomposes before melting)",
      "value": 400,
      "bound": "lower",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "basis": "decomposes before melting"
      },
      "method": "Printed as greater than 400 °C with the note decomposes before melting",
      "status": "ground",
      "source": "albemarle-tih2-n",
      "where": "Physical and chemical properties table, Melting point/range row",
      "source_detail": {
        "title": "Albemarle, Titanium Hydride, Grade N, technical data sheet (issue 2021-07-22)",
        "url": "https://www.albemarle.com/sites/default/files/2025-10/titanium-hydride-grade-n.PDF",
        "year": 2021,
        "kind": "datasheet",
        "license": "supplier technical data sheet, cited not reproduced"
      }
    },
    {
      "benchmark": "auto_ignition_temperature",
      "label": "Auto-ignition temperature, TiH2 powder",
      "value": 400,
      "bound": "lower",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "form": "powder, grade N, min. 99.9 % below 63 µm"
      },
      "method": "Printed as greater than 400 °C in the Albemarle grade N specification. The Sigma-Aldrich SDS gives no auto-ignition data",
      "status": "ground",
      "source": "albemarle-tih2-n",
      "where": "Specification table, Auto Ignition Temperature row",
      "source_detail": {
        "title": "Albemarle, Titanium Hydride, Grade N, technical data sheet (issue 2021-07-22)",
        "url": "https://www.albemarle.com/sites/default/files/2025-10/titanium-hydride-grade-n.PDF",
        "year": 2021,
        "kind": "datasheet",
        "license": "supplier technical data sheet, cited not reproduced"
      }
    },
    {
      "benchmark": "hydrogen_release_temperature",
      "label": "Hydrogen release onset, untreated TiH2",
      "value": 763,
      "bound": "exact",
      "unit": "K",
      "scope": "material",
      "conditions": {
        "basis": "approximately 763 K for untreated TiH2, as cited by the paper from Kennedy et al."
      },
      "method": "Secondhand figure quoted in the KTU paper introduction. Kept in kelvin as printed",
      "status": "ground",
      "source": "ktu-tih2-foam",
      "where": "Introduction, first paragraph",
      "source_detail": {
        "title": "Zhang et al., The Influence of Titanium Hydride Pretreatment on the Compressive Properties of Aluminum Foam, Materials Science (Medziagotyra) 20(4), 2014, doi 10.5755/j01.ms.20.4.6082",
        "url": "https://matsc.ktu.lt/index.php/MatSc/article/view/6082/4359",
        "year": 2014,
        "kind": "paper",
        "license": "open-access journal article, cited not reproduced"
      }
    },
    {
      "benchmark": "volume_change",
      "label": "Volume expansion on hydriding, TiH2",
      "value": 19,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "basis": "metal to hydride transformation, as printed for TiH2"
      },
      "method": "Printed in the ORNL introduction (e.g., 19% in the case of TiH2)",
      "status": "ground",
      "source": "ornl-zrh-2020",
      "where": "Section 1 Introduction, paragraph on volume expansion during hydriding",
      "source_detail": {
        "title": "Hu et al., ORNL/SPR-2020/1672, Fabrication of Zirconium Hydride with Controlled Hydrogen Loading (Oak Ridge National Laboratory)",
        "url": "https://info.ornl.gov/sites/publications/Files/Pub146553.pdf",
        "kind": "report",
        "license": "US Department of Energy report"
      }
    },
    {
      "benchmark": "hydrogen_density",
      "label": "Hydrogen density, TiH2",
      "value": 0.152,
      "bound": "exact",
      "unit": "g H/cm3",
      "scope": "material",
      "conditions": {
        "basis": "mass of hydrogen per volume of hydride, as tabulated"
      },
      "method": "Printed in ORNL Table 1, TiH2 row",
      "status": "ground",
      "source": "ornl-zrh-2020",
      "where": "Table 1, TiH2 row, g H/cm3 column",
      "source_detail": {
        "title": "Hu et al., ORNL/SPR-2020/1672, Fabrication of Zirconium Hydride with Controlled Hydrogen Loading (Oak Ridge National Laboratory)",
        "url": "https://info.ornl.gov/sites/publications/Files/Pub146553.pdf",
        "kind": "report",
        "license": "US Department of Energy report"
      }
    },
    {
      "benchmark": "moderating_ratio",
      "label": "Moderating ratio, TiH2",
      "value": 6.3,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "basis": "ratio of macroscopic slowing-down power to macroscopic neutron absorption cross section, as defined in the report"
      },
      "method": "Printed in ORNL Table 1, TiH2 row",
      "status": "ground",
      "source": "ornl-zrh-2020",
      "where": "Table 1, TiH2 row, Moderating ratio column",
      "source_detail": {
        "title": "Hu et al., ORNL/SPR-2020/1672, Fabrication of Zirconium Hydride with Controlled Hydrogen Loading (Oak Ridge National Laboratory)",
        "url": "https://info.ornl.gov/sites/publications/Files/Pub146553.pdf",
        "kind": "report",
        "license": "US Department of Energy report"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, ZrH2 powder, 25 °C",
      "value": 5.6,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "temperature": "25 °C",
        "form": "powder, grade PS"
      },
      "method": "Density printed in the Albemarle grade PS technical data sheet, with the note information taken from reference works and the literature",
      "status": "ground",
      "source": "albemarle-zrh-ps",
      "where": "Physical and chemical properties table, Density row",
      "source_detail": {
        "title": "Albemarle, Zirconium Hydride, Grade PS, technical data sheet",
        "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-ps.PDF",
        "kind": "datasheet",
        "license": "supplier technical data sheet, cited not reproduced"
      }
    },
    {
      "benchmark": "density",
      "label": "Hydride density, ZrH2, ORNL Table 1",
      "value": 5.56,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "basis": "hydride density as tabulated by ORNL"
      },
      "method": "Printed in ORNL Table 1, ZrH2 row, Hydride density column",
      "status": "ground",
      "source": "ornl-zrh-2020",
      "where": "Table 1, ZrH2 row, Hydride density column",
      "source_detail": {
        "title": "Hu et al., ORNL/SPR-2020/1672, Fabrication of Zirconium Hydride with Controlled Hydrogen Loading (Oak Ridge National Laboratory)",
        "url": "https://info.ornl.gov/sites/publications/Files/Pub146553.pdf",
        "kind": "report",
        "license": "US Department of Energy report"
      }
    },
    {
      "benchmark": "hydrogen_density",
      "label": "Hydrogen density, ZrH2",
      "value": 0.122,
      "bound": "exact",
      "unit": "g H/cm3",
      "scope": "material",
      "conditions": {
        "basis": "mass of hydrogen per volume of hydride, as tabulated"
      },
      "method": "Printed in ORNL Table 1, ZrH2 row",
      "status": "ground",
      "source": "ornl-zrh-2020",
      "where": "Table 1, ZrH2 row, g H/cm3 column",
      "source_detail": {
        "title": "Hu et al., ORNL/SPR-2020/1672, Fabrication of Zirconium Hydride with Controlled Hydrogen Loading (Oak Ridge National Laboratory)",
        "url": "https://info.ornl.gov/sites/publications/Files/Pub146553.pdf",
        "kind": "report",
        "license": "US Department of Energy report"
      }
    },
    {
      "benchmark": "moderating_ratio",
      "label": "Moderating ratio, ZrH2",
      "value": 55,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "basis": "ratio of macroscopic slowing-down power to macroscopic neutron absorption cross section, as defined in the report"
      },
      "method": "Printed in ORNL Table 1, ZrH2 row. ORNL calls ZrHx the most promising moderator on this ratio",
      "status": "ground",
      "source": "ornl-zrh-2020",
      "where": "Table 1, ZrH2 row, Moderating ratio column",
      "source_detail": {
        "title": "Hu et al., ORNL/SPR-2020/1672, Fabrication of Zirconium Hydride with Controlled Hydrogen Loading (Oak Ridge National Laboratory)",
        "url": "https://info.ornl.gov/sites/publications/Files/Pub146553.pdf",
        "kind": "report",
        "license": "US Department of Energy report"
      }
    },
    {
      "benchmark": "slowing_down_power",
      "label": "Slowing-down power, ZrH2",
      "value": 1.45,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "basis": "as tabulated by ORNL, dimensionless"
      },
      "method": "Printed in ORNL Table 1, ZrH2 row",
      "status": "ground",
      "source": "ornl-zrh-2020",
      "where": "Table 1, ZrH2 row, Slowing down power column",
      "source_detail": {
        "title": "Hu et al., ORNL/SPR-2020/1672, Fabrication of Zirconium Hydride with Controlled Hydrogen Loading (Oak Ridge National Laboratory)",
        "url": "https://info.ornl.gov/sites/publications/Files/Pub146553.pdf",
        "kind": "report",
        "license": "US Department of Energy report"
      }
    },
    {
      "benchmark": "volume_change",
      "label": "Volume expansion on hydriding, ZrH2",
      "value": 14.3,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "basis": "metal to ZrH2 transformation, as printed"
      },
      "method": "Printed in the ORNL introduction (14.3% in the case of ZrH2)",
      "status": "ground",
      "source": "ornl-zrh-2020",
      "where": "Section 1 Introduction, paragraph on volume expansion during hydriding",
      "source_detail": {
        "title": "Hu et al., ORNL/SPR-2020/1672, Fabrication of Zirconium Hydride with Controlled Hydrogen Loading (Oak Ridge National Laboratory)",
        "url": "https://info.ornl.gov/sites/publications/Files/Pub146553.pdf",
        "kind": "report",
        "license": "US Department of Energy report"
      }
    },
    {
      "benchmark": "hydrogen_content",
      "label": "Hydrogen content, ZrH2 grade PS, minimum",
      "value": 1.5,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "grade": "PS",
        "bound": "minimum"
      },
      "method": "Specification minimum printed in the Albemarle grade PS data sheet",
      "status": "ground",
      "source": "albemarle-zrh-ps",
      "where": "Specification table, H row",
      "source_detail": {
        "title": "Albemarle, Zirconium Hydride, Grade PS, technical data sheet",
        "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-ps.PDF",
        "kind": "datasheet",
        "license": "supplier technical data sheet, cited not reproduced"
      }
    },
    {
      "benchmark": "hydrogen_content",
      "label": "Hydrogen content, ZrH2 grade G, minimum",
      "value": 1.9,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "grade": "G",
        "bound": "minimum"
      },
      "method": "Specification minimum printed in the Albemarle grade G data sheet",
      "status": "ground",
      "source": "albemarle-zrh-g",
      "where": "Specification table, H row",
      "source_detail": {
        "title": "Albemarle, Zirconium Hydride, Grade G, technical data sheet",
        "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-g.PDF",
        "kind": "datasheet",
        "license": "supplier technical data sheet, cited not reproduced"
      }
    },
    {
      "benchmark": "dissociation_pressure",
      "label": "Dissociation pressure, epsilon ZrH1.85 at 800 °C",
      "value": 30,
      "bound": "exact",
      "unit": "atm",
      "scope": "material",
      "conditions": {
        "phase": "epsilon, ZrH1.85",
        "temperature": "800 °C"
      },
      "method": "Phase stability entry printed in the INL and Los Alamos overview. The slide gives no further detail",
      "status": "ground",
      "source": "inl-gain-2026",
      "where": "Phase stability slide, epsilon ZrH1.85 entry",
      "source_detail": {
        "title": "Kohnert, High Temperature Moderator Overview, 2026 MRP Review (INL GAIN, Los Alamos slides)",
        "url": "https://gain.inl.gov/content/uploads/4/2026/03/16-Kohnert_HighTemperatureModeratorOverview_2026-MRP-Review.pdf",
        "year": 2026,
        "kind": "report",
        "license": "DOE GAIN presentation, cited not reproduced"
      }
    },
    {
      "benchmark": "dissociation_pressure",
      "label": "Dissociation pressure, delta ZrH1.6 at 800 °C",
      "value": 1,
      "bound": "exact",
      "unit": "atm",
      "scope": "material",
      "conditions": {
        "phase": "delta, ZrH1.6",
        "temperature": "800 °C"
      },
      "method": "Phase stability entry printed in the INL and Los Alamos overview",
      "status": "ground",
      "source": "inl-gain-2026",
      "where": "Phase stability slide, delta ZrH1.6 entry",
      "source_detail": {
        "title": "Kohnert, High Temperature Moderator Overview, 2026 MRP Review (INL GAIN, Los Alamos slides)",
        "url": "https://gain.inl.gov/content/uploads/4/2026/03/16-Kohnert_HighTemperatureModeratorOverview_2026-MRP-Review.pdf",
        "year": 2026,
        "kind": "report",
        "license": "DOE GAIN presentation, cited not reproduced"
      }
    },
    {
      "benchmark": "hydrogen_evolution_onset",
      "label": "Hydrogen evolution onset, ZrH2",
      "value": 300,
      "bound": "lower",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "basis": "printed as evolves hydrogen above 300 °C"
      },
      "method": "Printed in the ATI safety data sheet, melting point and freezing point row",
      "status": "ground",
      "source": "ati-zrh-sds",
      "where": "Physical and chemical properties table, Melting point/freezing point row",
      "source_detail": {
        "title": "ATI, SAC050 Zirconium Hydride, safety data sheet (EU, Rev 2)",
        "url": "https://www.atimaterials.com/safety-data-sheets/Documents/EuropeanUnion/EU-EN/SAC/SAC050%20Zirconium%20Hydride%20EU-EN%20Rev2.pdf",
        "kind": "datasheet",
        "license": "supplier safety data sheet, cited not reproduced"
      }
    },
    {
      "benchmark": "density",
      "label": "Density, HfH2 powder, 20 °C",
      "value": 11.4,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "temperature": "20 °C",
        "form": "powder, grade PS (technical grade)"
      },
      "method": "Commercial powder specification printed on the Albemarle product page. It is not a measured value for pure stoichiometric HfH2",
      "status": "ground",
      "source": "albemarle-hfh-ps",
      "where": "Physical and chemical properties table, Density row",
      "source_detail": {
        "title": "Albemarle, Hafnium Hydride, Grade PS, product page with specifications and handling instructions",
        "url": "https://www.albemarle.com/au/en/product/hafnium-hydride-grade-ps",
        "kind": "datasheet",
        "license": "supplier product page, cited not reproduced"
      }
    },
    {
      "benchmark": "hydrogen_content",
      "label": "Hydrogen content, HfH2 grade PS, minimum",
      "value": 1,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "grade": "PS",
        "bound": "minimum"
      },
      "method": "Typical specification printed on the Albemarle product page",
      "status": "ground",
      "source": "albemarle-hfh-ps",
      "where": "Specifications list, H min row",
      "source_detail": {
        "title": "Albemarle, Hafnium Hydride, Grade PS, product page with specifications and handling instructions",
        "url": "https://www.albemarle.com/au/en/product/hafnium-hydride-grade-ps",
        "kind": "datasheet",
        "license": "supplier product page, cited not reproduced"
      }
    },
    {
      "benchmark": "molar_mass",
      "label": "Molar mass, HfH2 grade PS",
      "value": 180.5,
      "bound": "exact",
      "unit": "g/mol",
      "scope": "material",
      "conditions": {
        "basis": "molecular weight printed on the Albemarle product page"
      },
      "method": "Printed as 180.50 g/mol in the Albemarle physical and chemical properties table",
      "status": "ground",
      "source": "albemarle-hfh-ps",
      "where": "Physical and chemical properties table, Molecular Weight row",
      "source_detail": {
        "title": "Albemarle, Hafnium Hydride, Grade PS, product page with specifications and handling instructions",
        "url": "https://www.albemarle.com/au/en/product/hafnium-hydride-grade-ps",
        "kind": "datasheet",
        "license": "supplier product page, cited not reproduced"
      }
    },
    {
      "benchmark": "hydrogen_desorption_temperature",
      "label": "Hydrogen desorption step near 350 °C, HfH2-x",
      "value": 350,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "phase": "epsilon, HfH2-x",
        "method": "isochronal heating by thermogravimetry from 25 to 1000 °C"
      },
      "method": "Approximate step temperature printed in the Bangor abstract",
      "status": "ground",
      "source": "bangor-hfh",
      "where": "Abstract, first desorption region",
      "source_detail": {
        "title": "Pollard et al., Hydrogen desorption kinetics of hafnium hydride powders (Bangor University research output)",
        "url": "https://research.bangor.ac.uk/en/publications/hydrogen-desorption-kinetics-of-hafnium-hydride-powders/",
        "kind": "paper",
        "license": "journal article, abstract cited not reproduced"
      }
    },
    {
      "benchmark": "hydrogen_desorption_temperature",
      "label": "Hydrogen desorption step near 415 °C, HfH2-x",
      "value": 415,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "phase": "delta, HfH1.6-x",
        "method": "isochronal heating by thermogravimetry from 25 to 1000 °C"
      },
      "method": "Approximate step temperature printed in the Bangor abstract",
      "status": "ground",
      "source": "bangor-hfh",
      "where": "Abstract, second desorption region",
      "source_detail": {
        "title": "Pollard et al., Hydrogen desorption kinetics of hafnium hydride powders (Bangor University research output)",
        "url": "https://research.bangor.ac.uk/en/publications/hydrogen-desorption-kinetics-of-hafnium-hydride-powders/",
        "kind": "paper",
        "license": "journal article, abstract cited not reproduced"
      }
    },
    {
      "benchmark": "hydrogen_desorption_temperature",
      "label": "Hydrogen desorption step near 700 °C, HfH2-x",
      "value": 700,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "phase": "alpha, Hf",
        "method": "isochronal heating by thermogravimetry from 25 to 1000 °C"
      },
      "method": "Approximate step temperature printed in the Bangor abstract",
      "status": "ground",
      "source": "bangor-hfh",
      "where": "Abstract, third desorption region",
      "source_detail": {
        "title": "Pollard et al., Hydrogen desorption kinetics of hafnium hydride powders (Bangor University research output)",
        "url": "https://research.bangor.ac.uk/en/publications/hydrogen-desorption-kinetics-of-hafnium-hydride-powders/",
        "kind": "paper",
        "license": "journal article, abstract cited not reproduced"
      }
    },
    {
      "benchmark": "activation_energy",
      "label": "Kissinger activation energy, first desorption step, HfH2-x",
      "value": 150,
      "bound": "exact",
      "unit": "kJ/mol",
      "scope": "material",
      "conditions": {
        "phase": "epsilon, HfH2-x"
      },
      "method": "Approximate Kissinger value printed in the Bangor abstract",
      "status": "ground",
      "source": "bangor-hfh",
      "where": "Abstract, Kissinger analysis sentence",
      "source_detail": {
        "title": "Pollard et al., Hydrogen desorption kinetics of hafnium hydride powders (Bangor University research output)",
        "url": "https://research.bangor.ac.uk/en/publications/hydrogen-desorption-kinetics-of-hafnium-hydride-powders/",
        "kind": "paper",
        "license": "journal article, abstract cited not reproduced"
      }
    },
    {
      "benchmark": "activation_energy",
      "label": "Kissinger activation energy, second desorption step, HfH2-x",
      "value": 170,
      "bound": "exact",
      "unit": "kJ/mol",
      "scope": "material",
      "conditions": {
        "phase": "delta, HfH1.6-x"
      },
      "method": "Approximate Kissinger value printed in the Bangor abstract",
      "status": "ground",
      "source": "bangor-hfh",
      "where": "Abstract, Kissinger analysis sentence",
      "source_detail": {
        "title": "Pollard et al., Hydrogen desorption kinetics of hafnium hydride powders (Bangor University research output)",
        "url": "https://research.bangor.ac.uk/en/publications/hydrogen-desorption-kinetics-of-hafnium-hydride-powders/",
        "kind": "paper",
        "license": "journal article, abstract cited not reproduced"
      }
    },
    {
      "benchmark": "activation_energy",
      "label": "Kissinger activation energy, third desorption step, HfH2-x",
      "value": 90,
      "bound": "exact",
      "unit": "kJ/mol",
      "scope": "material",
      "conditions": {
        "phase": "alpha, Hf"
      },
      "method": "Approximate Kissinger value printed in the Bangor abstract",
      "status": "ground",
      "source": "bangor-hfh",
      "where": "Abstract, Kissinger analysis sentence",
      "source_detail": {
        "title": "Pollard et al., Hydrogen desorption kinetics of hafnium hydride powders (Bangor University research output)",
        "url": "https://research.bangor.ac.uk/en/publications/hydrogen-desorption-kinetics-of-hafnium-hydride-powders/",
        "kind": "paper",
        "license": "journal article, abstract cited not reproduced"
      }
    }
  ],
  "corrosion": [
    {
      "environment": "Oxidizing agents, acids and cold hydrofluoric acid",
      "headline": "TiH2 resists most reagents but oxidizing agents, acids and cold hydrofluoric acid attack it",
      "effect": "Albemarle says that like titanium metal, TiH2 resists most chemical reagents, but is attacked at elevated temperature by oxidizing agents and acids, and is attacked by cold hydrofluoric acid solutions. The rating moderate is the assistant's judgement from this statement. The sheet gives no test numbers.",
      "rating": "moderate",
      "conditions": {
        "basis": "statement in the handling section of the grade N data sheet"
      },
      "source": "albemarle-tih2-n",
      "where": "Handling and storage section"
    },
    {
      "environment": "Elevated temperature at low pressure",
      "headline": "TiH2 gives off hydrogen on heating, so hydrogen loss must be planned for",
      "effect": "Albemarle says that at elevated temperatures and low pressures the generation of hydrogen must be considered. The KTU paper gives 763 K as the release temperature for untreated TiH2 and reports that pre-treatment at 753 K for 30 min was best for aluminium foam. The rating moderate is the assistant's judgement; neither source rates it.",
      "rating": "moderate",
      "conditions": {
        "basis": "heating in the foaming process, and at low pressure per the data sheet"
      },
      "source": "ktu-tih2-foam",
      "where": "Introduction and Section 3.1 Structural features"
    },
    {
      "environment": "Air, fine powder at room temperature",
      "headline": "Fine ZrH2 powder burns slowly in air and must be kept from flames and sparks",
      "effect": "Albemarle grade PS calls the powder a highly flammable solid with a dust explosion hazard that burns slowly in air. The sheet gives the handling rules: keep away from flames, sparks and heat sources, and use ground-connected apparatus to avoid ignition by electrostatic discharge. The rating moderate is the assistant's judgement.",
      "rating": "moderate",
      "conditions": {
        "basis": "handling statement in the grade PS data sheet, no test data"
      },
      "source": "albemarle-zrh-ps",
      "where": "Handling row"
    },
    {
      "environment": "Heating above 300 °C, and reversible hydrogen loss in vacuum",
      "headline": "ZrH2 evolves hydrogen above 300 °C and its reaction runs back and forth in vacuum",
      "effect": "The ATI sheet says ZrH2 evolves hydrogen above 300 °C. Albemarle grade PS says it yields hydrogen by a reversible reaction in vacuum. The INL overview says the hydrogen pressure in the cladding gives a higher burst risk for ZrH than for YH, and that no thermal testing data exist for ZrH in cladding. The rating moderate is the assistant's judgement.",
      "rating": "moderate",
      "conditions": {
        "basis": "heating and vacuum statements from two suppliers, and the INL overview of reactor moderators"
      },
      "source": "ati-zrh-sds",
      "where": "Physical and chemical properties table, Melting point/freezing point row"
    },
    {
      "environment": "Air, fine powder at room temperature",
      "headline": "Fine HfH2 powder burns slowly in air and must not be fought with water",
      "effect": "Albemarle grade PS for hafnium hydride calls it a highly flammable solid with a dust explosion hazard that burns slowly in air. Its fire guidance is to cover only with sand, limestone or a dry class D powder, and the sheet says do not use water. The rating moderate is the assistant's judgement.",
      "rating": "moderate",
      "conditions": {
        "basis": "handling instructions on the product page, no test data"
      },
      "source": "albemarle-hfh-ps",
      "where": "Handling Instructions"
    },
    {
      "environment": "Heating from 25 to 1000 °C",
      "headline": "HfH2 gives off hydrogen in three steps near 350, 415 and 700 °C",
      "effect": "The Bangor study heats epsilon HfH2-x powder and finds three hydrogen release regions, one for each phase (epsilon HfH2-x, delta HfH1.6-x and alpha Hf). The study says hydrogen release degrades the moderating function, so the phase change matters for a moderator in service. The rating moderate is the assistant's judgement.",
      "rating": "moderate",
      "conditions": {
        "basis": "isochronal heating by thermogravimetry and X-ray diffraction; atmosphere not stated in the abstract"
      },
      "source": "bangor-hfh",
      "where": "Abstract, desorption regions and degradation sentence"
    }
  ],
  "risks": {
    "hazards": [
      {
        "text": "Sigma-Aldrich SDS: flammable solid, Category 1, hazard statement H228 (flammable solid), with the signal word Danger, and precautionary statement P241 (use explosion-proof electrical, ventilating and lighting equipment)",
        "ghs": [
          "H228"
        ],
        "source": "sigma-tih2",
        "where": "Section 2 Hazards identification; Section 2 Precautionary statements"
      },
      {
        "text": "Albemarle grade N: highly flammable solid, dust explosion hazard. In case of fire, cover with dry sand or dry chemical, never with water, carbon dioxide or halocarbon",
        "ghs": [],
        "source": "albemarle-tih2-n",
        "where": "Handling and storage section"
      },
      {
        "text": "ATI safety data sheet for zirconium hydride: flammable solids, Category 1, signal word Danger",
        "ghs": [],
        "source": "ati-zrh-sds",
        "where": "Section 2 Hazards identification, Label elements"
      },
      {
        "text": "Albemarle hafnium hydride: highly flammable solid, dust explosion hazard. Do not use water on a fire",
        "ghs": [],
        "source": "albemarle-hfh-ps",
        "where": "Handling Instructions"
      }
    ],
    "failure_risks": [
      {
        "mode": "Dust cloud or powder ignition",
        "trigger": "Powder dispersed in air near a flame, spark or electrostatic discharge",
        "consequence": "Albemarle warns of a dust explosion hazard and of sudden ignition by electrostatic discharge for the ZrH2 powder, and gives the same warning for TiH2 and HfH2",
        "severity": "high",
        "source": "albemarle-zrh-ps",
        "where": "Handling row"
      },
      {
        "mode": "Hydrogen release on heating, TiH2",
        "trigger": "Heating above about 763 K in a melt or at low pressure",
        "consequence": "The hydrogen released forms bubbles that become pores in aluminium foam. Early release before the aluminium melts causes crack-like pores and loss of foaming control",
        "severity": "moderate",
        "source": "ktu-tih2-foam",
        "where": "Introduction and Section 3 Results and discussion"
      },
      {
        "mode": "Cladding burst, ZrH moderator",
        "trigger": "High-temperature operation of a ZrH moderator in cladding",
        "consequence": "The INL overview says ZrH has a higher plenum pressure and a higher burst risk than YH, and that no thermal testing data for ZrH in cladding are known",
        "severity": "high",
        "source": "inl-gain-2026",
        "where": "Main operational differences between YH and ZrH slide"
      },
      {
        "mode": "Loss of moderating function, HfH2",
        "trigger": "Heating to about 350 °C and above",
        "consequence": "The Bangor abstract says hydrogen release leads to degradation of the moderating function of hafnium hydride",
        "severity": "moderate",
        "source": "bangor-hfh",
        "where": "Abstract, first paragraph"
      }
    ],
    "side_effects": [
      {
        "text": "At high temperature the hydrides release hydrogen, which is flammable. Albemarle and ATI both say that water on a fire can cause an explosion",
        "affects": "Equipment and people near a fire of hydride powder",
        "source": "ati-zrh-sds",
        "where": "Section 5 Extinguishing media"
      }
    ],
    "handling": [
      {
        "text": "Keep away from flames, sparks and heat sources. Use ground-connected metallic apparatus to avoid sudden ignition by electrostatic discharge. Wear gloves, a face shield or goggles (ZrH2 grade PS, HfH2 product page)",
        "source": "albemarle-zrh-ps",
        "where": "Handling row"
      },
      {
        "text": "Use explosion-proof electrical, ventilating and lighting equipment (P241), and provide exhaust ventilation where dust is formed",
        "source": "sigma-tih2",
        "where": "Section 7 Handling and storage"
      },
      {
        "text": "Packed dry under argon in tins of at most 5 kg (ZrH2 grade PS)",
        "source": "albemarle-zrh-ps",
        "where": "Packaging row"
      }
    ],
    "mitigations": [
      {
        "text": "Cover fires only with dry sand, limestone or a class D dry powder. Do not use water, carbon dioxide or halocarbon (TiH2 grade N, HfH2 product page)",
        "source": "albemarle-tih2-n",
        "where": "Handling and storage section"
      }
    ]
  },
  "uses": [
    {
      "application": "propulsion-and-tanks",
      "device": "Titanium hydride as a reservoir for pure hydrogen",
      "example": "Albemarle lists TiH2 as a reservoir for pure hydrogen and says it yields hydrogen at elevated temperatures in a reversible reaction. The ORNL report says metal hydrides have been seen as an efficient, low-risk option for dense hydrogen storage since the late 1970s.",
      "source": "albemarle-tih2-n",
      "where": "Application section; Handling row"
    },
    {
      "application": "radiation-shielding",
      "device": "Zirconium hydride moderator in SNAP and TRIGA reactors",
      "example": "The ORNL report names the SNAP program and TRIGA research reactors as users of ZrHx as a high-performance moderator. It ranks zirconium hydride as the most promising moderator of the hydrides it tabulates, on the moderating ratio.",
      "source": "ornl-zrh-2020",
      "where": "Section 1 Introduction, paragraph on moderator examples"
    },
    {
      "application": "radiation-shielding",
      "device": "Hafnium hydride neutron moderator and attenuator for compact reactors",
      "example": "The Bangor University abstract calls hafnium hydride a candidate neutron moderator and attenuator for compact nuclear reactors, where hydrogen release would reduce its moderating performance.",
      "source": "bangor-hfh",
      "where": "Abstract, first sentence"
    },
    {
      "application": "structures",
      "device": "Titanium hydride as a foaming agent for closed-cell aluminium foam",
      "example": "The KTU paper adds 1.5 wt% TiH2 to melted commercially pure aluminium and stirs it to make closed-cell foam with a porosity of about 80 %. The best pre-treatment was 753 K for 30 min.",
      "source": "ktu-tih2-foam",
      "where": "Section 2 Experimental, and Section 3.1 Structural features"
    },
    {
      "application": "structures",
      "device": "Hafnium and zirconium hydride grades as hydrogen sources for foaming metals and as alloying additions in powder metallurgy",
      "example": "Albemarle lists the hafnium hydride grade PS and the zirconium hydride grade PS as hydrogen sources for foaming metals and as alloying constituents in powder metallurgy.",
      "source": "albemarle-hfh-ps",
      "where": "Applications paragraph"
    }
  ],
  "supply": [
    {
      "subject": "Titanium (feedstock for TiH2)",
      "producers": [
        {
          "country": "China",
          "share_percent": 70.3,
          "year": 2025
        },
        {
          "country": "Japan",
          "share_percent": 14.3,
          "year": 2025
        },
        {
          "country": "Russia",
          "share_percent": 6.8,
          "year": 2025
        },
        {
          "country": "Kazakhstan",
          "share_percent": 4.3,
          "year": 2025
        },
        {
          "country": "Saudi Arabia",
          "share_percent": 3.2,
          "year": 2025
        }
      ],
      "critical_lists": [
        {
          "list": "EU critical raw materials list (titanium metal, as shown on the European Commission page)",
          "listed": true
        }
      ],
      "recycling": "USGS 2026: consumption data for titanium scrap metal for the titanium metal industry were withheld, because survey responses were limited.",
      "substitutes": [],
      "source": "usgs-mcs2026-titanium",
      "where": "World Sponge Metal Production table, 2025 column (world total 370,000 t); shares calculated by Space Mushroom from the printed tonnages. Recycling paragraph. Lists: EU page (see sources)"
    },
    {
      "subject": "Zirconium (feedstock for ZrH2)",
      "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
        },
        {
          "country": "Senegal",
          "share_percent": 5.8,
          "year": 2025
        }
      ],
      "critical_lists": [
        {
          "list": "EU critical raw materials list (zirconium is not in the list printed on the European Commission page)",
          "listed": false
        }
      ],
      "recycling": "USGS 2026: companies in Oregon and Utah recycled zirconium from new scrap generated during metal production. Refractories are often recycled but could not be quantified.",
      "substitutes": [],
      "source": "usgs-mcs2026-zirconium-hafnium",
      "where": "World Mine Production and Reserves table, zirconium mineral concentrates, 2025 column (world total 1,200 thousand t, gross weight); shares calculated by Space Mushroom from the printed tonnages. These are mine shares of concentrate, not sponge metal"
    },
    {
      "subject": "Hafnium (feedstock for HfH2)",
      "producers": [],
      "critical_lists": [
        {
          "list": "EU critical raw materials list (hafnium, as shown on the European Commission page)",
          "listed": true
        }
      ],
      "recycling": "USGS 2026: hafnium metal recycling was minimal.",
      "substitutes": [
        "USGS 2026: boron or cadmium-silver-indium alloys can substitute for hafnium metal in nuclear control rods, and zirconium can be used interchangeably with hafnium in certain superalloys."
      ],
      "source": "usgs-mcs2026-zirconium-hafnium",
      "where": "Hafnium paragraph of the USGS 2026 summary. The table gives no world primary hafnium production (the USGS text says the data were not available)"
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "Sigma-Aldrich safety data sheet, titanium hydride (archived copy hosted by Purdue University)",
      "type": "sds",
      "url": "https://www.physics.purdue.edu/primelab/safety/MSDS/SDS/titanium%20hydride%20%20-%20Aldrich.pdf"
    },
    {
      "title": "Albemarle technical data sheet, Titanium Hydride, Grade N (issue 2021-07-22)",
      "type": "datasheet",
      "url": "https://www.albemarle.com/sites/default/files/2025-10/titanium-hydride-grade-n.PDF",
      "year": 2021
    },
    {
      "title": "Albemarle technical data sheet, Titanium Hydride, Grade G",
      "type": "datasheet",
      "url": "https://www.albemarle.com/sites/default/files/documents/titanium-hydride-grade-g.PDF"
    },
    {
      "title": "Albemarle technical data sheet, Zirconium Hydride, Grade PS",
      "type": "datasheet",
      "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-ps.PDF"
    },
    {
      "title": "Albemarle technical data sheet, Zirconium Hydride, Grade G",
      "type": "datasheet",
      "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-g.PDF"
    },
    {
      "title": "Albemarle product page, Hafnium Hydride, Grade PS",
      "type": "datasheet",
      "url": "https://www.albemarle.com/au/en/product/hafnium-hydride-grade-ps"
    },
    {
      "title": "ATI safety data sheet, SAC050 Zirconium Hydride (EU, Rev 2)",
      "type": "sds",
      "url": "https://www.atimaterials.com/safety-data-sheets/Documents/EuropeanUnion/EU-EN/SAC/SAC050%20Zirconium%20Hydride%20EU-EN%20Rev2.pdf"
    },
    {
      "title": "ORNL/SPR-2020/1672, Fabrication of Zirconium Hydride with Controlled Hydrogen Loading (Table 1, metal hydride properties)",
      "type": "report",
      "url": "https://info.ornl.gov/sites/publications/Files/Pub146553.pdf"
    },
    {
      "title": "INL GAIN, High Temperature Moderator Overview (2026 MRP Review), Los Alamos slides",
      "type": "report",
      "url": "https://gain.inl.gov/content/uploads/4/2026/03/16-Kohnert_HighTemperatureModeratorOverview_2026-MRP-Review.pdf",
      "year": 2026
    },
    {
      "title": "Pollard et al., Hydrogen desorption kinetics of hafnium hydride powders (Bangor University research output)",
      "type": "paper",
      "url": "https://research.bangor.ac.uk/en/publications/hydrogen-desorption-kinetics-of-hafnium-hydride-powders/"
    },
    {
      "title": "Zhang et al., The Influence of Titanium Hydride Pretreatment on the Compressive Properties of Aluminum Foam, Materials Science (Medziagotyra) 20(4), 2014",
      "type": "paper",
      "url": "https://matsc.ktu.lt/index.php/MatSc/article/view/6082/4359",
      "year": 2014
    },
    {
      "title": "NIST atomic weights and isotopic compositions, Titanium",
      "type": "database",
      "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=Ti&ascii=html&isotype=some"
    },
    {
      "title": "PubChem compound record, titanium hydride (CID 197094), molecular formula and weight",
      "type": "database",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/197094"
    },
    {
      "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, Zirconium and Hafnium",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-zirconium-hafnium.pdf",
      "year": 2026
    }
  ],
  "gaps": [
    "Hardness, thermal conductivity, thermal expansion and elastic constants of TiH2, ZrH2 and HfH2 were not found in any page read in this run. They are left out.",
    "Melting point of ZrH2 and HfH2: no fetched source. The Albemarle sheets give decomposition, not melting.",
    "Crystal structure and space group were not read for TiH2 or ZrH2 in a fetched page, so the identity block has no crystal_system. The HfH2 structure is only in a first-principles paper, which is not used.",
    "Theoretical density of stoichiometric HfH2 and ZrH2 were not found. The HfH2 value of 11.4 g/cm3 is a commercial powder specification.",
    "Density conflict: TiH2 values are 3.91 g/cm3 (Albemarle, Sigma) and 3.78 g/cm3 (ORNL Table 1). Both are kept, each with its source.",
    "Crustal abundance of titanium, zirconium and hafnium was not read in a fetched page in this run, so supply has no abundance entry.",
    "USGS 2025 List of Critical Minerals: the USGS page could not be read in this run. Only the EU list is recorded for titanium, zirconium and hafnium.",
    "World primary hafnium production: the USGS 2026 summary says the data were not available, so no producer shares are given for hafnium.",
    "Production route of TiH2, ZrH2 and HfH2 (hydriding of the metal with hydrogen): the ORNL report gives the general method only, so the recipe names the metal and hydrogen without a process temperature.",
    "Atomic weight of hydrogen: NIST gives the standard atomic weight as the interval [1.00784, 1.00811]. The recipe uses 1.008, which lies inside the interval.",
    "Ageing under radiation, long-term vacuum storage, and space flight: no source read in this run. The SNAP reactor history is taken from the ORNL introduction only, not from a flight record.",
    "Hazard statements (H codes) for ZrH2 and HfH2: only the ATI sheet (flammable solids, Category 1, Danger) and the Albemarle handling text were read. American Elements' H315, H319 and H335 were seen in a search snippet only and are not used.",
    "Designations (UNS, EN, ASTM and others): no fetched page printed one for these hydrides, so none are listed. The CAS numbers are in identity.cas and in the properties source notes.",
    "Hydrogen release curves for TiH2 (the 450 to 560 C and 500 to 670 C pre-treatment figures) were seen in search snippets only and are not used. The 763 K figure is from the KTU paper, which cites Kennedy et al.",
    "Patent statements on ZrH dissociation pressure at 600 to 800 C in SNAP reactors were seen in search snippets only and are not used.",
    "Property names not in property-canon.yaml: hydrogen_content, hydrogen_density, hydrogen_release_temperature, hydrogen_evolution_onset, hydrogen_desorption_temperature, auto_ignition_temperature, slowing_down_power, moderating_ratio, dissociation_pressure, activation_energy, volume_change and molar_mass. Canonical units are used where the source printed them.",
    "Environments: no source read supports a space environment tag, so tags.environments is empty."
  ],
  "story": {
    "why": "Titanium hydride and its zirconium and hafnium relatives store a large amount of hydrogen in a dense solid. Albemarle sells TiH2 as a reservoir for pure hydrogen, a hydrogen source for foaming metals and an alloying aid in powder metallurgy. ZrH2 has long been the moderator of choice for compact reactors, because it combines a high moderating ratio (55 in ORNL Table 1) with hydrogen density. HfH2 is studied as a moderator and attenuator for compact reactors. The trade is that all three release hydrogen when heated, so their use depends on keeping the hydrogen in place.",
    "uses": [
      {
        "where": "Hydrogen reservoir",
        "line": "Albemarle says TiH2 is used as a reservoir for pure hydrogen and yields hydrogen at elevated temperatures in a reversible reaction. The ORNL report describes metal hydrides as a low-risk option for dense hydrogen storage."
      },
      {
        "where": "Reactor moderators",
        "line": "ORNL names the SNAP program and TRIGA reactors as users of zirconium hydride as a moderator. The Bangor abstract calls hafnium hydride a candidate moderator and attenuator for compact reactors."
      },
      {
        "where": "Foaming and powder metallurgy",
        "line": "The KTU paper foams commercially pure aluminium with 1.5 wt% TiH2 to a porosity of about 80 %. Albemarle lists the ZrH2 and HfH2 grades as hydrogen sources for foaming metals and as alloying additions in powder metallurgy."
      }
    ],
    "can_do": [
      {
        "label": "Hydrogen density",
        "line": "TiH2 holds 0.152 g of hydrogen per cm3 of hydride, and ZrH2 holds 0.122 g per cm3, both from ORNL Table 1.",
        "benchmark": "hydrogen_density",
        "scope": "material",
        "value": "0.152"
      },
      {
        "label": "Moderation",
        "line": "In ORNL Table 1, ZrH2 has a moderating ratio of 55 against 6.3 for TiH2. The ratio measures slowing-down power against neutron absorption.",
        "benchmark": "moderating_ratio",
        "scope": "material",
        "value": "55"
      },
      {
        "label": "Density",
        "line": "TiH2 has a density of 3.91 g/cm3 at 20 °C (Albemarle). ZrH2 is 5.6 g/cm3 at 25 °C and HfH2 is 11.4 g/cm3 at 20 °C (Albemarle grades).",
        "benchmark": "density",
        "scope": "material",
        "value": "3.91"
      }
    ],
    "compare": "The three hydrides are light and dense in hydrogen content, but they differ in density by a factor of about three. TiH2 is the least dense, which suits powder metallurgy. ZrH2 has the highest moderating ratio of the three tabulated in ORNL and it is the moderator in SNAP-type reactors. HfH2 is the densest and releases hydrogen in steps near 350, 415 and 700 °C. The three are compared on density, hydrogen content and hydrogen density because those are the values that all sources give.",
    "compare_rows": [
      {
        "label": "Density",
        "benchmark": "density",
        "scope": "material"
      },
      {
        "label": "Hydrogen content",
        "benchmark": "hydrogen_content",
        "scope": "material"
      },
      {
        "label": "Hydrogen density",
        "benchmark": "hydrogen_density",
        "scope": "material"
      }
    ],
    "handling": [
      "Keep the powder away from flames, sparks and heat. Use ground-connected equipment against electrostatic ignition (Albemarle).",
      "Avoid dust and use explosion-proof electrical equipment and exhaust ventilation where dust forms (Sigma-Aldrich P241).",
      "Fight a fire with dry sand, limestone or a class D powder. Do not use water (Albemarle, ATI)."
    ],
    "good_for": [
      "Hydrogen reservoirs and foaming agents, where a dense, stable powder that gives off hydrogen on heating is wanted (Albemarle, KTU).",
      "Compact-reactor moderators, where ZrH2 has a high moderating ratio (ORNL Table 1) and HfH2 is studied as a moderator and attenuator (Bangor)."
    ],
    "watch_out": [
      "Hydrogen loss on heating: TiH2 near 763 K, ZrH2 above 300 °C, and HfH2 in steps near 350, 415 and 700 °C.",
      "Dust explosion and flammability. All three are flammable solids and the powder is dangerous in a dust cloud.",
      "The density of TiH2 differs by source: 3.91 g/cm3 from Albemarle and Sigma, and 3.78 g/cm3 in ORNL Table 1."
    ],
    "verdict": "Metal hydride powders are a good hydrogen store and foaming agent, and ZrH2 is a proven reactor moderator. They give off hydrogen on heating and burn as dust, so each use needs the hydrogen kept in place and the powder kept from ignition. Melting, hardness, thermal conductivity and flight data are not sourced here.",
    "recipe": {
      "line": "TiH2, ZrH2 and HfH2 each have one metal atom and two hydrogen atoms per formula unit. The metal is bonded to hydrogen in a hydride lattice that expands on hydriding (ORNL). The common preparation is direct reaction of the metal with hydrogen gas, guided by the phase diagram (ORNL); no process temperature for these grades was sourced.",
      "parts": [
        {
          "name": "Titanium",
          "symbol": "Ti",
          "role": "Metal in TiH2. NIST gives 47.867 (1).",
          "atoms": 1,
          "atomic_weight": 47.867
        },
        {
          "name": "Zirconium",
          "symbol": "Zr",
          "role": "Metal in ZrH2. NIST gives 91.224 (2).",
          "atoms": 1,
          "atomic_weight": 91.224
        },
        {
          "name": "Hafnium",
          "symbol": "Hf",
          "role": "Metal in HfH2. NIST gives 178.49 (2).",
          "atoms": 1,
          "atomic_weight": 178.49
        },
        {
          "name": "Hydrogen",
          "symbol": "H",
          "role": "Stored in the lattice and released on heating. NIST gives [1.00784, 1.00811] as the standard atomic weight, so 1.008 is used.",
          "atoms": 2,
          "atomic_weight": 1.008
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "The three powders are sold as highly flammable solids with a dust-explosion hazard. The supplier sheets give the handling rules and the fire guidance.",
        "points": [
          {
            "label": "Ignition",
            "line": "The Sigma-Aldrich SDS classifies TiH2 as a flammable solid with H228. Keep it away from flames, sparks and heat sources."
          },
          {
            "label": "Dust",
            "line": "Albemarle warns of a dust explosion hazard for TiH2, ZrH2 and HfH2. Avoid dust and provide exhaust ventilation where dust is formed."
          },
          {
            "label": "Fire",
            "line": "Cover a fire only with dry sand, limestone or a class D powder. Do not use water, carbon dioxide or halocarbon."
          }
        ],
        "level": 0,
        "verdict": "Flammable powder with a dust-explosion risk"
      },
      {
        "title": "If a powder or part heats up",
        "lead": "These results come from the sources listed, not from incidents.",
        "points": [
          {
            "label": "TiH2",
            "line": "The KTU paper gives 763 K as the release temperature for untreated TiH2, and says that pre-treatment at 753 K for 30 min is the most suitable for aluminium foam."
          },
          {
            "label": "ZrH2",
            "line": "ATI says ZrH2 evolves hydrogen above 300 °C. The INL overview gives a 30 atm dissociation pressure for the epsilon phase at 800 °C."
          },
          {
            "label": "HfH2",
            "line": "The Bangor study finds hydrogen release near 350, 415 and 700 °C in three steps."
          }
        ]
      },
      {
        "title": "Handling and storage",
        "points": [
          {
            "label": "Storage",
            "line": "Store dry and closed. ZrH2 grade PS is packed dry under argon in tins of at most 5 kg."
          },
          {
            "label": "Electrostatic discharge",
            "line": "Use ground-connected metallic apparatus to avoid sudden ignition by electrostatic discharge (Albemarle)."
          }
        ]
      }
    ]
  },
  "updated": "2026-10-26",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 31,
    "unreachable": 3,
    "caveats": 9,
    "note": "Written in this run from pages read in this run: the Sigma-Aldrich TiH2 SDS, Albemarle TiH2 grades N and G, Albemarle ZrH grades PS and G, Albemarle HfH2 product page, the ATI ZrH2 SDS, the ORNL ZrH report (Table 1), the INL GAIN moderator slides, the Bangor HfH2 abstract, the KTU TiH2 foaming paper, the USGS 2026 titanium and zirconium-hafnium summaries, the EC critical raw materials page, NIST atomic weights and PubChem CID 197094. Unreachable: USGS 2025 critical minerals page (no readable text), and the NASA NTRS record for the 2021 moderator paper (download failed). Hafnium production and ZrH2 melting point not found."
  },
  "sources": {
    "sigma-tih2": {
      "title": "Sigma-Aldrich, Safety data sheet for titanium hydride (archived copy hosted by Purdue University)",
      "url": "https://www.physics.purdue.edu/primelab/safety/MSDS/SDS/titanium%20hydride%20%20-%20Aldrich.pdf",
      "kind": "datasheet",
      "license": "supplier safety data sheet, cited not reproduced"
    },
    "albemarle-tih2-n": {
      "title": "Albemarle, Titanium Hydride, Grade N, technical data sheet (issue 2021-07-22)",
      "url": "https://www.albemarle.com/sites/default/files/2025-10/titanium-hydride-grade-n.PDF",
      "year": 2021,
      "kind": "datasheet",
      "license": "supplier technical data sheet, cited not reproduced"
    },
    "albemarle-tih2-g": {
      "title": "Albemarle, Titanium Hydride, Grade G, technical data sheet",
      "url": "https://www.albemarle.com/sites/default/files/documents/titanium-hydride-grade-g.PDF",
      "kind": "datasheet",
      "license": "supplier technical data sheet, cited not reproduced"
    },
    "albemarle-zrh-ps": {
      "title": "Albemarle, Zirconium Hydride, Grade PS, technical data sheet",
      "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-ps.PDF",
      "kind": "datasheet",
      "license": "supplier technical data sheet, cited not reproduced"
    },
    "albemarle-zrh-g": {
      "title": "Albemarle, Zirconium Hydride, Grade G, technical data sheet",
      "url": "https://www.albemarle.com/sites/default/files/documents/zirconium-hydride-grade-g.PDF",
      "kind": "datasheet",
      "license": "supplier technical data sheet, cited not reproduced"
    },
    "albemarle-hfh-ps": {
      "title": "Albemarle, Hafnium Hydride, Grade PS, product page with specifications and handling instructions",
      "url": "https://www.albemarle.com/au/en/product/hafnium-hydride-grade-ps",
      "kind": "datasheet",
      "license": "supplier product page, cited not reproduced"
    },
    "ati-zrh-sds": {
      "title": "ATI, SAC050 Zirconium Hydride, safety data sheet (EU, Rev 2)",
      "url": "https://www.atimaterials.com/safety-data-sheets/Documents/EuropeanUnion/EU-EN/SAC/SAC050%20Zirconium%20Hydride%20EU-EN%20Rev2.pdf",
      "kind": "datasheet",
      "license": "supplier safety data sheet, cited not reproduced"
    },
    "ornl-zrh-2020": {
      "title": "Hu et al., ORNL/SPR-2020/1672, Fabrication of Zirconium Hydride with Controlled Hydrogen Loading (Oak Ridge National Laboratory)",
      "url": "https://info.ornl.gov/sites/publications/Files/Pub146553.pdf",
      "kind": "report",
      "license": "US Department of Energy report"
    },
    "inl-gain-2026": {
      "title": "Kohnert, High Temperature Moderator Overview, 2026 MRP Review (INL GAIN, Los Alamos slides)",
      "url": "https://gain.inl.gov/content/uploads/4/2026/03/16-Kohnert_HighTemperatureModeratorOverview_2026-MRP-Review.pdf",
      "year": 2026,
      "kind": "report",
      "license": "DOE GAIN presentation, cited not reproduced"
    },
    "bangor-hfh": {
      "title": "Pollard et al., Hydrogen desorption kinetics of hafnium hydride powders (Bangor University research output)",
      "url": "https://research.bangor.ac.uk/en/publications/hydrogen-desorption-kinetics-of-hafnium-hydride-powders/",
      "kind": "paper",
      "license": "journal article, abstract cited not reproduced"
    },
    "ktu-tih2-foam": {
      "title": "Zhang et al., The Influence of Titanium Hydride Pretreatment on the Compressive Properties of Aluminum Foam, Materials Science (Medziagotyra) 20(4), 2014, doi 10.5755/j01.ms.20.4.6082",
      "url": "https://matsc.ktu.lt/index.php/MatSc/article/view/6082/4359",
      "year": 2014,
      "kind": "paper",
      "license": "open-access journal article, cited not reproduced"
    },
    "usgs-mcs2026-titanium": {
      "title": "USGS Mineral Commodity Summaries 2026, Titanium and Titanium Dioxide",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-titanium.pdf",
      "kind": "report",
      "license": "public domain (USGS)"
    },
    "usgs-mcs2026-zirconium-hafnium": {
      "title": "USGS Mineral Commodity Summaries 2026, Zirconium and Hafnium",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-zirconium-hafnium.pdf",
      "kind": "report",
      "license": "public domain (USGS)"
    },
    "ec-crm": {
      "title": "European Commission, Critical raw materials (list of critical raw materials, including titanium metal and hafnium)",
      "url": "https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en",
      "kind": "web",
      "license": "European Commission web page"
    },
    "nist-atomic-weights": {
      "title": "NIST, Atomic weights and isotopic compositions for hydrogen, titanium, zirconium and hafnium",
      "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=Ti&ascii=html&isotype=some",
      "kind": "database",
      "license": "NIST public data"
    },
    "pubchem-tih2": {
      "title": "PubChem compound record, titanium hydride (CID 197094)",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/197094",
      "kind": "database",
      "license": "public domain (NCBI)"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/titanium-hydride/"
}