Zirconium hydride (ZrH2) ZrH2
ZrH2 · CAS 7704-99-6
Also known as Zirconium Hydride, Grade G
Zirconium hydride (ZrH2) is a grey-black powder of zirconium and hydrogen, with two hydrogen atoms for each zirconium atom in the formula.
Evidence level
2 of 5
Lab-measured
- 0Predicted only. No one has made it, or no measurement exists.
- 1Calculated. Only calculated or predicted values from sources.
- 2Lab-measured. Measured properties with their conditions stated.
- 3Space-relevant tests. Measured in conditions relevant to space, such as vacuum or atomic oxygen.
- 4Ground-qualified. Qualified for an application on the ground.
- 5Flown or field-proven. Flight or field results exist.
Recipe, share of the weight
- Zr not statedZirconium
- H not statedHydrogen
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)
Risk at a glance
- People No data. No hazard data recorded
- If it fails High. Dust ignition
- Corrosion Moderate. Sources disagree on whether zirconium hydride reacts with water. Both say that any gas released is flammable.
Quick facts: ZrH2
| Property | Value | Basis |
|---|---|---|
| Density | 5.6 g/cm³ | 1 sourced value |
What is the density of Zirconium hydride (ZrH2)?
Zirconium hydride (ZrH2) has a density of 5.6 g/cm³. The source and test conditions are listed in the properties table on this page.
What is Zirconium hydride (ZrH2) used for?
Uses recorded in the sources include Hydrogen source for foaming metals; Moderator block in a nuclear thermal propulsion reactor (conceptual reference design, not flown); Getter material (the device is not named in the datasheet).
Why it exists
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.
Where it's used
Metal foaming
The datasheet names zirconium hydride as a hydrogen source for the foaming of metals. PubChem also lists its use as a metal foaming agent.
Space nuclear propulsion
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.
Getters and pyrotechnics
Albemarle makes this grade for highly effective getters, which are activated by dehydrogenation, and for illumination effects in pyrotechnics.
Research reactor fuel (a different material)
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.
Recipe
ZrH2
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 %.
| Ingredient | Share of the weight | What it does |
|---|---|---|
| Zirconium Zr | not stated | The metal framework. NIST prints a standard atomic weight of 91.224 for zirconium. |
| Hydrogen H | not stated | 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. |
Weight shares are as printed in the sources.
What it can do
Hydrogen foaming
Supplies hydrogen for foaming metals, the datasheet's stated application.
Getter
Works as a getter material once it is activated by dehydrogenation, as the datasheet describes.
Moderation
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.
How it compares
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.
The same measurements for each material, so you can compare them. Each row names the key condition under the value; the full conditions and methods are in the numbered notes under Technical details.
| Measurement | ZrH2 |
|---|---|
| Physical and electrical | |
| Density, Grade G at 25 °C | 5.6 g/cm³1 |
| Bulk density of the powderRange printed in the manufacturer's datasheet | 1000 to 2000 kg/m3 |
| Relative density of cold-pressed disks | 73 % of theoretical density12 |
| Temperature behavior | |
| Decomposition temperature (decomposes before melting) | > 400 °C2 |
| Ignition point of the powder | 200 to 310 °C8 |
| Other measurements | |
| Molecular weight | 93.24 g/mol3 |
| Zirconium plus hafnium content (minimum) | > 97.6 %4 |
| Hafnium content (natural)Value printed in the manufacturer's datasheet | 2 % |
| Hydrogen content (minimum) | > 1.9 %5 |
| Iron impurity (maximum) | < 0.08 %6 |
| Silicon impurity (maximum) | < 0.5 %7 |
| Water solubility | < 8×10^-5 g/l9 |
| Average particle size (Blaine) | 5.5 µm10 |
| Share of powder finer than 45 µm (minimum)Printed in the datasheet as min. 99.9 % < 45 µm | > 99.9 % |
| Weight gain on combustion | 31.8 %11 |
| Stated purity of a micron powder | > 99.5 %13 |
Why choose it, and why not
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 for
- 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.
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.
Technical details
For scientists and researchers. Everything above comes from the record below: every number with its method, its conditions and its source.
Other names and standards
The same grade under other systems, as datasheets and standards print them. Each code was checked against the page it comes from.
| System | Codes |
|---|---|
| Trade name | Zirconium Hydride, Grade G |
Notes
The method, full conditions and any caveat for the numbered rows above.
| # | Measurement | Method | Conditions | Caveat |
|---|---|---|---|---|
| 1 | Density, Grade G at 25 °C | 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 | temperature 25 °Cgrade Zirconium Hydride, Grade G (product numbers 10000387, 10001973, 10001974) | 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). |
| 2 | Decomposition temperature (decomposes before melting) | Printed in the datasheet as > 400 °C; the datasheet gives no melting point | grade Grade G powdernote in source Decomposes before melting | — |
| 3 | Molecular weight | Value printed in the manufacturer's technical data sheet | formula ZrH2 | — |
| 4 | Zirconium plus hafnium content (minimum) | Specification minimum printed in the manufacturer's datasheet | grade Grade Gtolerance +/- 0.5 % as printedbasis Zr + Hf, the datasheet's wording | — |
| 5 | Hydrogen content (minimum) | Specification minimum printed in the manufacturer's datasheet | basis minimum hydrogen content as printed in the specification | — |
| 6 | Iron impurity (maximum) | Specification maximum printed in the manufacturer's datasheet | basis maximum impurity as printed | — |
| 7 | Silicon impurity (maximum) | Specification maximum printed in the manufacturer's datasheet | basis maximum impurity as printed | — |
| 8 | Ignition point of the powder | Range printed in the manufacturer's datasheet under Additional Physical Properties | form powder, Grade G | — |
| 9 | Water solubility | Printed in the datasheet as < 0.00008 g/l at 23 °C | temperature 23 °Ctest OECD Test Guideline 29, as printed | — |
| 10 | Average particle size (Blaine) | Printed in the datasheet as average particle size acc. to Blaine | method printed Blainetolerance +/- 1 µm as printed | — |
| 11 | Weight gain on combustion | Printed in the datasheet under Additional Physical Properties | basis weight increase by combustion, as the datasheet defines ittolerance +/- 0.7 % as printed | — |
| 12 | Relative density of cold-pressed disks | Density calculated by the authors from the weight and dimensions of the pressed disk | form cold-pressed disk of zirconium hydride (ZrHx) powder, commercial 99 % purity, 50 meshpressure 400 MPa | 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. |
| 13 | Stated purity of a micron powder | Stated in the product title and specification table of a reseller's product page | grade micron powder, size printed as 1-10 µm on the reseller pagedefinition not defined on the page | 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. |
Corrosion and compatibility
What happens when it meets other materials and environments.
| Environment | Concern | What happens |
|---|---|---|
| Water, or humid air | moderate | Sources disagree on whether zirconium hydride reacts with water. Both say that any gas released is flammable.1 |
| Heating in air | moderate | Heated in air, the powder incandesces and can give mild explosions.2 |
| Dry, sealed storage | none | The datasheet gives an unlimited shelf life for dry, sealed storage.3 |
| # | Environment | Details | Test conditions |
|---|---|---|---|
| 1 | Water, or humid air | 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. | water temperature and exposure time not statedform powder |
| 2 | Heating in air | 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. | basis heating in air, no exposure time stated |
| 3 | Dry, sealed storage | 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. | packaging dry, in sealed tin canscondition dry storage |
Risks and side effects
Hazards to people, what happens when a cell overheats, and how the material is handled and stored.
For people
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.
- The powder
- PubChem's GHS summary gives H228 (flammable solid), H315 (skin irritation) and H319 (serious eye irritation), with the signal word Danger.
- Dust
- The datasheet warns of a dust explosion hazard. It gives an ignition point of 200 to 310 °C for the powder.
- Water
- 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.
In a fire
The fire guidance comes from the ERG 2024 entry for this compound, which PubChem reproduces.
- What to use
- Use dry sand, dry chemical, soda ash or lime. PubChem's ERG notes say do not use water or foam.
- Fire products
- Fire gives off irritating, corrosive and/or toxic gases, and runoff can contaminate the environment.
Handling and storage
- Storage
- The datasheet says to store the powder dry in tightly closed containers. It gives the product an unlimited shelf life under those conditions.
- Static
- Use ground-connected metal equipment. The datasheet warns of sudden ignition from electrostatic discharge.
- Transport
- Shipped as UN 1437, Class 4.1, flammable solid, Packing Group II.
Test details
The original wording and numbers from the sources, for readers who want them.
Failure risks
| Failure | Trigger and consequence |
|---|---|
| Dust ignitionhigh severity | Powder dust formed during handling or transfer, or an open flame or spark nearbyThe 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. |
| Reaction with waterhigh severity | Contact with water, including water sprayed on a fireFlammable 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. |
| Hydrogen loss on heatingmoderate severity | Heating above the decomposition temperatureThe 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. |
Side effects on surrounding parts
| Affects | Effect |
|---|---|
| Responders and nearby people | Fire produces irritating, corrosive and/or toxic gases (ERG 2024, Guide 138). |
| Waterways near the site | Runoff from fire control or dilution water may cause environmental contamination (ERG 2024, Guide 138). |
Handling and storage
- 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.
- Datasheet: store dry in tightly closed tin cans. The datasheet says the product has an unlimited shelf life.
- 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.
Mitigations
- Fight fires with dry sand or dry powder only, and never with water. PubChem's ERG notes say do not use water or foam.
- Use ground-connected metallic equipment to prevent sudden ignition by electrostatic discharge.
Supply and geography
How common the raw materials are and where they come from.
Zirconium (from zircon and zirconium mineral concentrates)
- Top producers (2025)
- Australia 33.3%, South Africa 22.5%, Mozambique 13.3%, China 8.3%
- 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.
Documents
Datasheets, safety data sheets, papers and standards you can open.
Full record
The complete spore, as stored. Free to reuse under CC-BY-4.0. Images keep the licence shown with each one.
Show the full YAML
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.
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
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.
designations:
- system: Trade name
code: Zirconium Hydride, Grade G
source: albemarle-zrh-g
where: Title of the technical data sheet
tags:
applications:
- structures
- propulsion-and-tanks
- electronics-and-chips
properties:
- benchmark: density
label: Density, Grade G at 25 °C
value: 5.6
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
- 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
- benchmark: molecular_weight
label: Molecular weight
value: 93.24
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
- 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
- benchmark: hafnium_content
label: Hafnium content (natural)
value: 2
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
- 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
- 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
- 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
- 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)
- 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
- 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
- benchmark: average_particle_size
label: Average particle size (Blaine)
value: 5.5
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
- 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
- benchmark: gain_on_ignition
label: Weight gain on combustion
value: 31.8
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)
- benchmark: relative_density
label: Relative density of cold-pressed disks
value: 73
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'
- 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'
checked_values: 16
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.'
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.
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
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).
story:
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
atoms: 1
atomic_weight: 91.224
role: The metal framework. NIST prints a standard atomic weight of 91.224 for zirconium.
- 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
verdict: Flammable solid; irritant; reacts with water
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.
- title: In a fire
verdict: 'Fire fighting: dry sand or powder only, never water'
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.
- title: Handling and storage
verdict: Keep dry and sealed; ground all equipment
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.
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.
- label: Getter
line: Works as a getter material once it is activated by dehydrogenation, as the datasheet describes.
- 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.
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
- label: Decomposition temperature
benchmark: decomposition_temperature
- label: Ignition point
benchmark: ignition_temperature
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.
References
Every number above carries a reference number. Click one to see the source and where in it the value comes from.
| # | Source | Type | Year | Used for |
|---|---|---|---|---|
| Zirconium Hydride, Grade G: technical data sheet | datasheet | 2021 | 24 values | |
| PubChem compound record, Zirconium hydride (CID 4137802) | database | 2026 | 9 values | |
| Mineral Commodity Summaries 2026: Zirconium and Hafnium | report | 2026 | 1 value | |
| Applicability Study of Hydride Materials (section 41), NIFS Annual Report 2013 | report | 2013 | 1 value | |
| High-Temperature Thermodynamic Functions for Zirconium and Unsaturated Zirconium Hydrides | paper | 1963 | 0 values | |
| Space Nuclear Propulsion Fuel and Moderator Development Plan: Conceptual Testing Reference Design | report | 2021 | 1 value | |
| TRIGA Type U-ZrH Cladding Steady State Mechanical Limitations (slides) | report | 2009 | 0 values | |
| Zirconium Hydride (ZrH2) Micron Powder, Purity 99.5+% (reseller product page) | web | 2026 | 1 value | |
| Atomic Weights and Isotopic Compositions for All Elements | database | 2026 | 0 values |
Updated