Zirconium is a chemical element. Zirconium is a lustrous,
gray-white, , strong transition metal that resembles titanium. Zirconium is used as an alloying agent due to its high resistance to corrosion. It is never found as a native metal; it is obtained mainly from the mineral zircon, which can be purified by chlorine.
Zirconium has no known biological role. Zirconium forms both inorganic and organometallic compounds such as zirconium dioxide and zirconocene dichloride, respectively. There are five naturally-occurring isotopes, three of which are stable. Short-term exposure to zirconium powder causes minor irritation, and inhalation of zirconium compounds can cause skin and lung granulomas.
Zirconium's excellent resistance to corrosion, it is often used as an alloying agent in materials that are exposed to corrosive agents, such as surgical appliances, explosive primers, vacuum tube getters and filaments. 90% of all zirconium produced is used in nuclear reactors because of its low neutron-capture cross-section and resistance to corrosion. Zirconium alloys are used in space vehicle parts for their resistance to heat, an important quality given the extreme heat associated with atmospheric reentry. Zirconium is also a component in some abrasives, such as grinding wheels and sandpaper. Zirconium is used in weapons such as the BLU-97/B Combined Effects Bomb for incendiary effect. Zirconium in the oxidized form is also used in dentistry for crowning of the teeth because of its biocompatibility, strength and appearance.
A major use of zirconium is for structural material in
nuclear reactor cores. Because of its low thermal neutron absorption cross-section and good strength, Zirconium is ideal in this application. The thermal neutron absorption cross-section is the ability of a material to absorb thermal neutrons. The lower the thermal neutron absorption, the greater the efficiency of a nuclear reactor. In this application, reactor grade (low hafnium) material must be used. The major nuclear grade Zircadyne alloys are: Zircaloy-2, Zircaloy-4, Zr-2.5Nb which have excellent corrosion resistance to high temperature steam and water, and good mechanical strength.
The most important zirconium compound, the zircon, is used as
refractory material for mould-casting, as abrasive and as constituent of insulating materials, enamels and other resistant to the temperature materials. It is also used as an artificial semi-precious stone, imitating diamond. Zirconium oxide is used as refractory material in the production of piezoelectric crystals and rings of high frequency induction reels, due to its low resistance to high temperature. It is still used as pigment in the ceramic industry. More than 80% of the produced zirconium is consumed in the form of these two compounds.
Other zirconium compounds have interesting properties and important applications. Thus, the carbide and the nitride with their high hardness, are used in producing abrasives and sharp edged instruments; the hydride is an hydrogen source and can be used as moderator in nuclear reactors; the double ammonium carbide and zirconile are used in preparing hydrophobic fluids and water-proof coatings; the phosphate, the molybdate and the tungstate are used as ion permuters, especially selective for alkali metals.
Metallic zirconium is the best construction material for nuclear reactors due to its low neutron cross section, high mechanical and chemical resistance and appropriate thermal conductivity. It is also used in the manufacture of zircaloy alloys that contain tin, iron and chromium in small amounts. Other smaller applications include flash production for photography, explosive, fireworks, tracer bullets, small rockets, etc.
