History and Applications of Zirconium

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ZrSiO4, which is a natural silicate containing zirconium called zircon or hyacinth, is widely distributed in nature, with a variety of beautiful colors from orange to red, considered as precious stones since ancient times. It is said that the term zircon comes from “Zarqūn” in Arabic referring to cinnabar, but another version that the term derives from “Zargun” in Persian meaning golden, while hyacinth comes from “Lily” in Greek. Sri Lanka, an island in the Indian Ocean, is rich in zircon.

In 1789, German M.H. Klaproth found something when studied on zircon. He firstly melted zircon and sodium hydroxide together and dissolved cooling substance with hydrochloric acid; and then added potassium carbonate into the solution, precipitated, filtered and washed the precipitate; finally boiled the precipitate with sulfuric together and filtered off silicon oxide. Later, he found no calcium, magnesium, aluminum oxide in the filtrate, but the precipitate appeared after the addition of potassium carbonate in the solution. However, the precipitate is unlike alumina that is soluble in alkali solution as well as it is unlike magnesium oxide that is able to react with acid, so he thought this precipitate was not the same as oxides which previously known, but constituted by Zirkonerde (zirconia, German). Soon, the French chemist de Morueau and Vauquelin both confirmed that his analysis was correct, so the element had its Latin name as zirconium and symbol as Zr. In 1808, British H. Davy decomposed zirconium compounds by the current, without success. In 1824, Sweden J.J. Berzelius first obtained zirconium metal by the reduction K2ZrF6 with potassium, but the product was not pure enough. The equation is: K2ZrF6 +4K = Zr +6KF, this reaction can also use Na as a reducing agent. Until 1914, two researchers Lely and Ham bruger from a Dutch manufacturer of metal incandescent lamp obtained pure zirconium metal through heating anhydrous zirconium tetrachloride with an excess of sodium metal in an empty ball up to 500°C by electric current.

Zirconium’s application in metallurgy

Zirconium is known as “vitamin” in the metallurgical industry, for its powerful deoxidation, denitrification and desulfuration. As long as steel is added to one-thousandth of zirconium, its hardness and strength will be strikingly improved. Armor steel, stainless steel and heat-resistant steel containing zirconium are important materials for the manufacture of defense weapons such as armored vehicles, tanks, artillery and armor plates. Blending copper with zirconium and making into copper wire, its electric conductivity is not weakened, but the melting point is greatly improved, so it is very suitable for the use of high-voltage wire. Zirc-magnesium alloy containing zirconium is light and heat resistant, with intensity twice than common magnesium alloys, used in the production of jet engines members.

In addition, with low ignition point and fast burning velocity, zirconium powder can be used as detonating explosive of detonators which could explode even underwater. Zirconium metal powder gives off blinding glare when it burns up with oxidant, so it is an ideal material to produce tracer bullets and flares. Meanwhile, it is used as a getter in electric vacuum, while as a heat source in the thermal battery. Usually, zirconium powder can be made by hydrogenation of zirconium sponge, fine grinding and dehydrogenation, as well as with CaH2 reducing ZrO2. Zirconium powder made by the second way has little chlorine so that it is more suitable for a getter than zirconium powder made by the first way. Zirconium powder with grain size of 2-3 microns is prone to reacts with oxygen resulting in spontaneous combustion and explosion, so it must pay attention to safety in the packaging, transportation and use.

Zirconium mineral resource distribution

Zirconium is generally considered as a rare metal. In fact, its content in the earth’s crust is quite large, more than common metals such as zinc, copper and tin. Zirconium ore reserves are highly concentrated in terms of geographical distribution. The world’s zirconium ore reserves are mainly in the hands of Australia, South Africa, Ukraine, India and Brazil. These five countries account for 86% of global zirconium ore resources, with very obvious resource monopoly. According to the U.S. Geological Survey statistics, China has only 500,000 tons of zirconium ore reserves, less than 1% zirconium ore resources all over the world.