Silver Rare Metals Hafnium Hf Nuclear Control Rod Material CAS 7440-58-6

Hafnium (Hf): Nuclear Control Rod Material, Heat-Resistant Alloys, and Vacuum Getter

Chemical formula: Hf, Atomic number: 72, Atomic weight: 178.49. It is a lustrous silver-gray transition metal with six naturally stable isotopes: Hf-174, 176, 177, 178, 179, and 180. It is resistant to dilute hydrochloric acid, sulfuric acid, and strong alkaline solutions, but dissolves in hydrofluoric acid and aqua regia.

Metallic hafnium is silver-gray with metallic luster. It has two allotropes:

• α-Hf: Hexagonal close-packed structure (1750°C), with higher transformation temperature than zirconium.
• β-Hf: High-temperature allotropic form exists.

Hafnium has high neutron absorption cross-section, making it suitable for reactor control materials. Two crystal structures:

• Below 1300°C: Hexagonal close-packed (α-form)
• Above 1300°C: Body-centered cubic (β-form)

It is a malleable metal that becomes hard and brittle when containing impurities. Stable in air, only surface darkens when heated. Thin filaments can be ignited by match flame. Properties resemble zirconium. Doesn't react with water, dilute acids or strong alkalis, but dissolves easily in aqua regia and hydrofluoric acid. Mainly exhibits +4 oxidation state in compounds. Hf alloy (Ta4HfC5) has the highest known melting point (~4215°C).

Applications

1. For manufacturing heat-resistant alloys.
2. For neutron absorption in nuclear industry.
3. For manufacturing getters.

Product Series

Health and Safety Information

Packaging Specifications

• Standard packaging: 50 kg/drum, 500 kg/pallet, ton bags
• Sample packaging: 500 g/bag, 1 kg/bottle

About Hafnium 
It can be prepared by magnesium reduction of hafnium tetrachloride or thermal decomposition of hafnium tetrachloride. HfCl4 and K2HfF6 can also be used as raw materials. It is produced by electrolysis in NaCl-KCl-HfCl4 (or K2HfF6) molten salts, following similar processes to zirconium production.

Hafnium mostly coexists with zirconium with no independent deposits. Current production uses crude hafnium oxide (HfO2) separated during zirconium processing. HfO2 is extracted using ion exchange resin methods, then metallic hafnium is prepared using same methods as zirconium.

Hafnium is valuable for its electron emission properties (e.g. incandescent lamp filaments). Used as X-ray tube cathodes, with tungsten or molybdenum alloys as high-voltage discharge tube electrodes. Commonly used in X-ray cathodes and tungsten filament manufacturing. Pure hafnium is ductile, easy to process, heat- and corrosion-resistant, making it important for nuclear energy industry. With large thermal neutron capture cross-section, it's ideal for neutron absorption. Used as control rods and protective devices in nuclear reactors. Hafnium powder serves as rocket propellant. In electrical industry, used for X-ray tube cathodes. Hf alloys protect rocket nozzles and re-entry vehicle surfaces. Hf-Ta alloys manufacture tool steels and resistor materials. As additive in heat-resistant alloys, hafnium is incorporated into tungsten, molybdenum and tantalum alloys. Hafnium carbide's high hardness and melting point make it suitable for hard alloy additives. Ta4HfC5 has ~4215°C melting point - highest known. In gas-filled systems, hafnium functions as getter to remove oxygen, nitrogen and other unwanted gases. In high-risk operations, hafnium additives prevent hydraulic fluid evaporation due to its strong anti-volatility, making it ideal for industrial and medical hydraulic fluids.