Hafnium

Hafnium bits

Hafnium(IV) oxide

Zircão

Hafnium ebeam remelted

Hafnium pellets with a thin oxide layer

Hafnium is a chemical element with the symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Its existence was predicted by Dmitri Mendeleev in 1869, though it was not identified until 1923 by Dirk Coster and George Charles de Hevesy, making it the last stable element to be discovered. Hafnium is named after Hafnia, the Latin name for Copenhagen, where it was discovered.

Properties

Hafnium is a heavy, ductile metal with a high melting point of approximately 2233°C (4051°F). It has a high corrosion resistance, making it an excellent material for use in the upper atmospheres of aircraft and in applications requiring high temperature resistance. It is not found free in nature but in minerals such as zirconium silicate (ZrSiO4). Despite its chemical similarity to zirconium, hafnium is sufficiently different to warrant its own classification in the periodic table.

Applications

Hafnium's primary use is in the nuclear industry due to its ability to absorb neutrons without forming long-lived radioactivity, making it an ideal material for use in nuclear reactors as control rods. It is also used in the manufacturing of semiconductors, where it serves as a gate material in field-effect transistors, improving the insulation between components at the nanoscale. Additionally, hafnium is used in high-temperature alloys and ceramics, owing to its strong resistance to corrosion and high melting point.

Occurrence and Production

Hafnium is found in most zirconium minerals, from which it is difficult to separate due to their chemical similarity. The most common method of extraction is through the Kroll process, which involves the reduction of the chloride form of the element with magnesium. This process yields pure hafnium and zirconium metals. The global production of hafnium is limited, with major producers including the United States, France, and Russia.

Isotopes

Hafnium has several isotopes, with hafnium-178 being the most abundant. It has a mix of stable and radioactive isotopes, with the latter being used in various scientific research applications, including geochronology and neutron capture therapy in medicine.

Health and Safety

While hafnium is not considered highly toxic, its dust and fumes can be hazardous if inhaled, causing irritation to the skin, eyes, and respiratory system. Proper safety precautions, such as wearing protective gear and ensuring adequate ventilation, are recommended when handling hafnium in powdered form or during processes that produce its fumes.

See Also

• Transition metal
• Periodic table
• Nuclear reactor
• Semiconductor