Zirconium

Zirconium is a lustrous, greyish-white transition metal. It is identified by the chemical symbol Zr and atomic number 40. This metal is solid at room temperature and is both ductile and malleable. These properties mean it can be stretched into wires or hammered into sheets. One of its most important traits is being highly corrosion-resistant. It can withstand exposure to acids, alkalis, and salt water.

Most zirconium comes from a silicate mineral called zircon. The name is related to the Persian word zargun, which means "gold-like." Zirconium also appears in over 140 other minerals, such as baddeleyite and eudialyte. In many cases, zirconium is produced as a byproduct of mining tin and titanium. Currently, there are over 60 million tonnes of zircon resources worldwide. Annual global production of zirconium is approximately 900,000 tonnes.

Extracting pure zirconium is a complex process. Most zirconium is produced through the reduction of zirconium(IV) chloride using magnesium metal. This is known as the Kroll process. After this, the metal is sintered to make it ductile enough for metalworking. Because this reduction process is so difficult, zirconium metal is much more expensive than the raw zircon mineral.

In industrial settings, scientists often must separate zirconium from hafnium. These two elements are chemically very similar. However, they behave very differently in nuclear environments. Hafnium has a neutron absorption cross-section 600 times greater than zirconium. This means hafnium soaks up neutrons, while zirconium does not. To separate them, engineers use liquid-liquid extraction. They exploit how hafnium derivatives dissolve differently in certain solvents. Another method involves fractional crystallization of potassium hexafluorozirconate.

Zirconium has a long history of discovery. In 1789, Martin Klaproth analyzed a mineral from Ceylon and identified the element. He called it Zirkonerde. In 1808, the scientist Humphry Davy attempted to isolate the metal using electrolysis, but he was unsuccessful. It was not until 1824 that Berzelius obtained an impure form of the metal. By 1925, manufacturers were able to produce zirconium at a large scale.

This metal is vital for high-technology applications. Because of its low neutron absorption, zirconium alloys are used to clad nuclear fuel rods. It is also used in space vehicles and turbine blades. These parts require high heat resistance. Zirconium has a very high melting point of 1855 °C. Its boiling point is even higher at 4409 °C.

Zirconium also creates many useful chemical compounds. Zirconium dioxide, or zirconia, is a common white solid. It is very tough and is used as a thermal barrier coating. It is even used as a substitute for diamonds. Organometallic compounds like zirconocene dichloride are also important. These are used in Ziegler–Natta catalysts to produce polypropylene.

Finally, zirconium is found in many unexpected places. It is used in dental implants, prosthetics, and water purification systems. It can even be found in deodorants and flashbulbs. In nature, zirconium is the 18th most abundant element in the Earth's crust. It is also found in the sun, meteorites, and even lunar rocks from the Apollo missions. While the metal is generally safe, the powder form is highly flammable and can cause eye irritation.