Zirconium fluoride

Three binary zirconium fluorides Zrp2, ZrF, and ZrF, are known to exist. The most important compounds industrially are zirconium tetrafluoride, ZrF, and fluorozirconic acid [12021 -95-3], H2ZrF, and its salts (see Zirconiumand zirconium compounds). 

Hafnium tetrafluoride [13709-52-9] is one component in the cladding layer of a proposed zirconium fluoride glass optical waveguide fiber composition which is expected to have a lower intrinsic light absorption than fused quart2 optical fiber (see Glass Fiber optics Fluorine compounds, inorganic-zirconium). 

Photochlorination of tetrachloroethylene, observed by Faraday, yields hexachloroethane [67-72-1]. Reaction with aluminum bromide at 100°C forms a mixture of bromotrichloroethane and dibromodichloroethane [75-81-0] (6). Reaction with bromine results in an equiUbrium mixture of tetrabromoethylene [79-28-7] and tetrachloroethylene. Tetrachloroethylene reacts with a mixture of hydrogen fluoride and chlorine at 225—400°C in the presence of zirconium fluoride catalyst to yield l,2,2-trichloro-l,l,2-trifluoroethane [76-13-1] (CFG 113) (7). 

Interfering cations, except aluminium and zirconium, can be removed by passage through an ion exchange column. In the presence of interfering anions and also aluminium and zirconium, fluoride may be separated as hydrofluorosilicic acid by distilling with dilute perchloric acid at 135 °C (temperature maintained by the addition of water) in the presence of a few glass beads. 

Jons Jakob Berzelius (1779-1848) produced the element by heating a mixture of potassium and potassium zirconium fluoride. 

Calcium metal is used in the reduction of zirconium fluorides, thorium and uranium oxides to obtain the metals. 

Magnesium chloride and excess magnesium are removed by distillation at reduced pressure. Pure zirconium may be prepared by several methods that include iodide decomposition process, zone refining, and electron beam melting. Also, Zr metal may be electrorefined in a molten salt bath of potassium zirconium fluoride, K2ZrFe... 

K. Kobayashi, T. Shigematsu, Trace determination of iron, cobalt, nickel and copper in zirconium fluoride by substoichiometric radioactivation analysis, J. Radioanal. Nucl. Chem. Articles 113 (1987) 333-341. 

In 1808 Sir Humphry Davy tried in vain to decompose zirconia with the electric current, but Berzelius (36) finally obtained the metal in 1824 by heating a dry mixture of potassium and potassium zirconium fluoride in a very small closed iron tube placed inside a platinum crucible. After the quiet reaction had taken place, he cooled the tube and placed it in distilled water, whereupon, to use his own words, There fell from the tube a black powder as fast as the salt dissolved, and at the same time there was evolved a small quantity of hydrogen.. . . The zirconium obtained in this manner is easily deposited. It can be washed with water without oxidizing. Washed and dried, it forms a black powder resembling charcoal, which cannot be compressed nor polished like a metal (15). 

Zirconium fluoride reacts with liquid ammonia, forming the unstable compound, ammino-zirconium tetrafluoride, 2ZrF42NH3. Zirconium tetrachloride forms several ammines. 

Calcium serves as a reductant for such reactive metals as zirconium, thorium, vanadium, and uranium. In zirconium reduction, zirconium fluoride is reacted with culcium metal. The high heat of the reaction melts the zirconium. The zirconium ingot resulting is remelted undet vacuum for purilicatinn. Thorium and uranium oxides are reduced with an excess of calcium in reactors or trays under an atmosphere of argon. The resulting tnetals are leached with acetic acid tu remove the lime. 

Finally, the chemistry of zirconium fluorides should be mentioned. This is a rather special case but does have some relevance to industrial usage, as discussed later. Zirconium fluorides exhibit a marked reluctance to hydrolyse at acid pHs. These zirconium fluoride derivatives tend to be less polymeric, although some polymeric nature is believed to exist [3]. 

Lithographic printing plates. Zirconium fluorides, such as potassium zirconium hexafluoride, are used to surface-treat anodized aluminium lithographic printing plates to give improved corrosion resistance of the subsequently treated plate [7],... 

Aluminium drinking carts. There are many patents [8] referring to the use of fluorozirconic acid (H2ZrF6)-based systems to treat the surface of aluminium cans to improve the corrosion resistance of the metal and the adhesion of the applied coatings. Typically, the zirconium fluoride will be used in conjunction with polyacrylic acid, presumably to form a complex in situ which acts as an adhesion promoter. Such surface treatment of aluminium is not restricted to zirconium fluorides, as ammonium zirconium carbonate displays similar properties in such application areas. 

The zirconium fluoride phosphate has a microporous 3D structure similar to that found in some aluminophosphate molecular sieves. 

Figure 6.5-5 Transmission for some IR-fibers (Im in length). (A) Zirconium fluoride (Fiber System, 1991), (B) chalcogenide (Fiber Systems, 1991), (C) silver halide (Ceram Optec, 1991).

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