40 Zr 91.224

Zr - Zirconium

Chemical Element Zirconium Melting Point °C 1852
Chemical Symbol Zr Boiling Point °C 4377
Atomic Number 40 Density g/cm3 6.5
Atomic Weight 91.224 Oxide ZrO2

Properties

Zirconium is a strong, durable metal. It is hard, lustrous and silvery in colour. Zirconium is a transition metal and is a member of Group 4 of the Periodic Table, the 18th most abundant element within the Earth’s crust. Zirconium reacts rapidly with oxygen within the air, forming a tough zirconium oxide layer on its surface protecting it from further reaction. This oxide layer makes zirconium very corrosion resistant. Zirconium does not dissolve in acids (except hydrofluoric acid) or alkalis. Powdered Zirconium is black, and it will burn in air if ignited, and zirconium dust is regarded as a dangerous fire hazard.

History

Zirconium was discovered in 1789 by German chemist, Martin Heinrech Klaproth, who at the time was analysing a zircon, which is a semi-precious gem. Zircon, along with hyacinth, jacinth and jargon, were known during biblical times and were thought to be inferior kinds of diamond.  This was proven to be untrue with the discovery of zirconium. This was not Klaproth’s only discovery that year, as he also discovered uranium, both later to be linked to the nuclear power industry. Klaproth was unable to isolate the metal himself and, unfortunately, did not live to see this achievement. It was not until 1824 that the element was isolated, by the Swedish chemist Jons Jacob Berzelius.

Sources

In order to reach metallic form, zircon sand is reduced via a solvent process using magnesium and chlorine to create low hafnium zirconium sponge for the nuclear industry. Consequently, producing companies are few, grouped around the historic nuclear energy producing nations of France (Cezus-Areva), USA (Wah Chang) and Russia (Chepetsky Mechanical Works). China is a new addition to this club, but is not expected to produce consistent nuclear grade material before 2015.  The quantity of zirconium available to the market in metal form is about 6,000 mt per year.

Uses

In the minor metals industry, the growth of non-nuclear applications has been the main driver.  Metal produced via the Van Arkel method, which results in crystal bars of high grade zirconium, are required in small amounts for super alloys, while 4% zirconium content of Zr sponge is required in titanium alloy (6Al-2Sn-4Zr-2Mo) for aerospace parts. Zirconium is also used in some aluminium alloys for aerospace, as well as in the car industry for engine blocks, while an alloy of CuCrNiZr is used to replace BeCu in contacts.  An alloy called Liquidmetal™ used in tennis rackets and other sports equipment is said to contain more than 60% zirconium.

For all these uses the non-nuclear industry relies on the nuclear sector for off-cuts and scrap, which are brought back into the loop and priced according to relative levels of tin (Sn), niobium (Nb), nitrogen (N), oxygen (O) and hafnium (Hf) content, as well as size and form.  The highest purity (and highest priced) zirconium metal is the Van Arkel material, which is today only made in Russia.  While plans exist in Russia to move from Van Arkel and Electron Beam zirconium metal to production of zirconium sponge, final execution of this project is thought to be a number of years away.  Only China brings the likelihood of reducing the supply deficit of available nuclear grade metal, while Russian origin crystal bar will always be more desirable for super alloy making.

References
  • Emsley, John. Nature’s Building Blocks, An A-Z Guide to the Elements, New Edition, Oxford University Press, 2011
  • Gray, Theodore. The Elements, A Visual Exploration of Every Known Atom in the Universe, Black Dog & Leventhal Publishers, Inc, NY, 2009
  • Stwertka, Albert. A Guide to the Elements, 3rd Edition, Oxford University Press, 2012

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