What are some common uses of zirconium

Zirconium


Author: H. Lohninger

Atomic number40
symbolZr
CAS no.7440-67-7
Atomic weight91,224 amu
Electron configuration[Kr] 4d2 5s2
Melting point1855 ° C
boiling point4409 ° C
density6,506 g / cm3
Sources: Enghag 2004 , Wieser 2011
history
M.H. In 1789 Klaproth discovered zirconium as an oxide in zircon, ZrSiO4. Elemental zirconium was first discovered in 1824 by J.J. Berzelius by reducing K2ZrF6 isolated with potassium. In 1925 A.E. van Arkel and J.H. de Boer to produce high-purity zirconium for the first time using the Van Arkel de Boer process named after them.
Occurrence
Zirconium does not occur naturally, but mainly as silicate (zircon) and as dioxide (zircon earth). Although zirconium occurs much more frequently than e.g. copper (see frequency table of the elements), it is usually unprofitable to mine due to its low concentration. Deposits worthy of mining are exclusively secondary deposits that have arisen through weathering and flooding. Interestingly, basaltic lunar rocks brought back from the Apollo missions have a surprisingly high zirconium content (up to 1000 ppm, the average content in the earth's crust is 165 ppm). Zirconium minerals always contain a few percent hafnium.
Presentation and extraction
To produce metallic zirconium, zirconium chloride is reduced with magnesium in a helium atmosphere (Kroll process). The zirconium can then be further purified using the Van Arkel de Boer process. However, the commercial zirconium obtained in this way contains a few percent hafnium, which cannot be separated off in this way.
properties
Zirconium is a silvery-gray shiny metal that can be easily deformed in its pure form. However, even traces of embedded foreign atoms (N, H, C, O) make the metal hard and brittle. In the air, zirconium develops a very thin passivating oxide layer, making it corrosion-resistant. In finely divided form, zirconium is oxidized in air at moderate temperatures.

Zirconium has a low cross-section for neutrons, which is why it is used as a cover for fuel rods. Since hafnium has a 600 times higher cross-section than zirconium, it has to be laboriously freed from hafnium for these purposes with the help of ion exchangers, fractional distillation or extraction processes (90% of the zirconium produced worldwide is used in nuclear reactors).

Zirconium-niobium alloys are superconducting and remain so when strong magnetic fields are applied. They were therefore used for superconducting magnets, but niobium-titanium alloys are now used for them.

use
Because of its corrosion resistance, zirconium is used in the chemical industry, e.g. for heat exchangers, stirrers or spinnerets. It is also used in nuclear technology (see above). Zirconia is used for laboratory equipment and refractories. Pure crystalline zirconia ("zircon") has a high refractive index and is used as a gemstone.