zircon sands - 02

Zirconium ( /zərˈkoʊniəm/ zər-KOH-ni-əm) is a chemical element with the symbol Zr and atomic number 40. Its atomic mass is 91.224. It is a lustrous, grey-white, strong transition metal that resembles titanium. Zirconium is used as an alloying agent for its strong resistance to corrosion. It is never found as a native metal; it is obtained mainly from the mineral zircon, which can be purified with chlorine. Zirconium was first isolated in an impure form in 1824 by Jöns Jakob Berzelius.
Detailed description
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.

Characteristics
Zirconium is a lustrous, grayish-white, soft, ductile, and malleable metal which is solid at room temperature, though it becomes hard and brittle at lower purities.[4][5] In powder form, zirconium is highly flammable, but the solid form is far less prone to ignition. Zirconium is highly resistant to corrosion by alkalis, acids, salt water, and other agents.[6] However, it will dissolve in hydrochloric and sulfuric acid, especially when fluorine is present.[7] Alloys with zinc become magnetic below 35 K.[6]
Zirconium's melting point is at 1855°C, and its boiling point 4409°C.[6] Zirconium has an electronegativity of 1.33 on the Pauling scale. Of the elements within d-block, zirconium has the fourth lowest electronegativity after yttrium, lutetium, and hafnium.[8]
Applications
Because of 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. Zirconium dioxide (ZrO2) is used in laboratory crucibles, metallurgical furnaces, as a refractory material,[6] and it can be sintered into a ceramic knife. Zircon (ZrSiO4) is cut into gemstones for use in jewelry. Zirconium carbonate (3ZrO2•CO2•H2O) was used in lotions to treat poison ivy, but this was discontinued because it occasionally caused bad skin reactions.[4]
Ninety percent of all zirconium produced is used in nuclear reactors (in the form of zircaloys) because of its low neutron-capture cross-section and resistance to corrosion.[5][6] Zirconium alloys are used in space vehicle parts for their resistance to heat, an important quality given the extreme heat associated with atmospheric reentry.[9] Zirconium is also a component in some abrasives, such as grinding wheels and sandpaper.[10] Zirconium is used in weapons such as the BLU-97/B Combined Effects Bomb for incendiary effect.
High temperature parts such as combustors, blades and vanes in modern jet engines and stationary gas turbines are to an ever increasing extent being protected by thin ceramic layers which reduce the metal temperatures below and keep them from undergoing (too) extensive deformation which could possibly result in early failure. They are absolutely necessary for the most modern gas turbines which are driven to ever higher firing temperatures to produce more electricity at less CO2. These ceramic layers are usually composed by a mixture of zirconium and yttrium oxide.[11]
Refining
Upon being collected from coastal waters, the solid mineral zircon is purified by spiral concentrators to remove excess sand and gravel and by magnetic separators to remove ilmenite and rutile. The byproducts can then be dumped back into the water safely, as they are all natural components of beach sand. The refined zircon is then purified into pure zirconium by chlorine or other agents, then sintered until sufficiently ductile for metalworking.[5] Zirconium and hafnium are both contained in zircon and they are quite difficult to separate due to their extremely similar chemical properties.[9] Usually, an ion exchange process is used to separate them.
History
The zirconium-containing mineral zircon, or its variations (jargoon, hyacinth, jacinth, ligure), were mentioned in biblical writings.[6][9] The mineral was not known to contain a new element until 1789,[10] when Klaproth analyzed a jargoon from the island of Ceylon (now Sri Lanka) in the Indian Ocean. He named the new element Zirkonerde (zirconia).[6] Humphry Davy attempted to isolate this new element in 1808 through electrolysis, but failed.[4] Zirconium (from Syriac ܙܐܪܓܥܢܥ zargono,[12] Arabic zarkûn ئشقنعى from Persian zargûn زرگون meaning "gold like")[9] was first isolated in an impure form in 1824 by Berzelius by heating a mixture of potassium and potassium-zirconium fluoride in a small decomposition process conducted in an iron tube.[6] These words were adapted into German Zirkon which became the source of the English words: Zircon and Zirconium. [13]
The crystal bar process (or Iodide process), discovered by Anton Eduard van Arkel and Jan Hendrik de Boer in 1925, was the first industrial process for the commercial production of pure metallic zirconium. The process involved thermally decomposing zirconium tetraiodide. It was superseded in 1945 by the much cheaper Kroll process developed by William Justin Kroll, in which zirconium tetrachloride is broken down by magnesium.[5][14]