Ammonium zirconium fluoride

Zirconium is readily attacked by acidic solutions containing fluorides. As Httle as 3 ppm flouride ion in 50% boiling sulfuric acid corrodes zirconium at 1.25 mm/yr. Solutions of ammonium hydrogen fluoride or potassium hydrogen fluoride have been used for pickling and electropolishing zirconium. Commercial pickling is conducted with nitric—hydrofluoric acid mixtures (see Metal surface treatments). 

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. 

During the 1970s, aqueous solutions containing tin(IV) chloride and ammonium bifluoride found commercial application as flame-resistant treatments for woollen sheepskins and rugs, " - where they had the advantage over competitive titanium and zirconium fluoride systems of not imparting any yellow... 

It was originally separated from zirconium by repeated recrystallization of the double ammonium or potassium fluorides by von Hevesey and Jantzen. Metallic hafnium was first prepared by van Arkel and deBoer by passing the vapor of the tetraiodide over a heated tungsten filament. Almost all hafnium metal now produced is made by reducing the tetrachloride with magnesium or with sodium (Kroll Process). 

Assay of beryUium metal and beryUium compounds is usuaUy accompHshed by titration. The sample is dissolved in sulfuric acid. Solution pH is adjusted to 8.5 using sodium hydroxide. The beryUium hydroxide precipitate is redissolved by addition of excess sodium fluoride. Liberated hydroxide is titrated with sulfuric acid. The beryUium content of the sample is calculated from the titration volume. Standards containing known beryUium concentrations must be analyzed along with the samples, as complexation of beryUium by fluoride is not quantitative. Titration rate and hold times ate critical therefore use of an automatic titrator is recommended. Other fluotide-complexing elements such as aluminum, sUicon, zirconium, hafnium, uranium, thorium, and rate earth elements must be absent, or must be corrected for if present in smaU amounts. Copper-beryUium and nickel—beryUium aUoys can be analyzed by titration if the beryUium is first separated from copper, nickel, and cobalt by ammonium hydroxide precipitation (15,16). 

The Preparation of Ammonium HeptafluozirconateflV). In a platinum bowl, dissolve 20 g of zirconium(IV) oxide in a hot 40% hydrogen fluoride solution taken in an excess of 20% relative to the calculated amount needed to convert the zirconium(IV) oxide to the tetrafluoride. Cool the solution in a bath with ice to 5 °C and filter it through a paper filter (preliminarily cover the funnel with a thin layer of paraffin). 

Calculate the amount of ammonium fluoride needed to convert the zirconium tetrafluoride to ammonium heptafluozirconate, and weigh a three-fold excess of the substance (why should the excess ammonium fluoride be taken ). Dissolve the ammonium fluoride in a minimum amount of water (see Appendix 1, Table 1), filter the solution, and add it to the zirconium tetrafluoride solution. If no ammonium heptafluozirconate precipitate appears, add 10-20 ml of ethanol. Filter ofi the precipitate with the aid of a Buchner funnel, rinse it several times on the filter with ethanol, and dry it in the air. 

For less activated aromatic systems (those without a nitro substituent), the halogcn-ex-changc reaction has been investigated with potassium fluoride in a variety of polar aprotic solvents in the presence or absence of a catalyst (see Table 13). Many different types of catalysts have been investigated these include crown ethers, quaternary ammonium salts, 3,164 pjjos-phonium salts, aminophosphonium salts, compounds containing a phosphorus and an amino function, and inorganic fluorides of boron, aluminum, tin, phosphorus, titanium and zirconium. Different forms of potassium fluoride have been used these include spray-dried potassium fluoride, freeze-dried potassium fluoride, potassium fluoride recryslal-lized from methanol, and potassium fluoride dispersed on caleium fluoride. ... 

With fluorine zirconium forms ZrF, when the oxide is heated with ammonium fluoride or when the chloride is treated with hydrogen fluoride. At 60° its solution begins to suffer hydrolysis, but on evaporating a solution containing free HF. a deposit is obtained to which the formula ZrF4 - 3 E O was formerly applied. It has some properties of a salt of this composition, but its behavior seems to indicate a composition ZrOF2 2 HF 2 H20.2... 

Another example of chemical decladding is afforded by the Zirflex process, which was proposed for zircaloy-clad UOj fuel before mechanical decladding was fully developed. In the Zirflex process [S17], zirconium or zircaloy cladding is dissolved as ammonium fluozirconate in a boiling solution of ammonium fluoride containing ammonium nitrate, the latter added to reduce hydrogen evolution. Overall reaction is approximately... 

Because of limited solubility of the ammonium fluozirconate product, there is an optimum NH4F concentration, around 5.5 Af, with an initial molar ratio of fluoride to zirconium between 6.5 and 7.0. 

ZIRCAT (7440-67-7) Finely divided material is spontaneously flammable in air may ignite and continue to bum under water. Violent reactions with oxidizers, alkali hydroxides, alkali metals (and their compounds), carbon tetrachloride, cupric oxide, lead, lead oxide, lead peroxide (combined material can burn explosively, and is sensitive to friction and static electricity), nitryl fluoride, oxygen difluoride, phosphoms, potassium, potassium compounds (potassium chlorate, potassium nitrate), sodium borate, sodium hydroxide. Explodes if mixed with hydrated borax when heated. Contact with lithium chromate may cause explosion above 752°F/450°C. Forms explosive mixture with potassium chlorate. Dusts of zirconium ignite and explode in a carbon dioxide atmosphere. Contact with ammonium-V-nitrosophenylhydroxylamine above 104°F/40°C forms an explosive material. Incompatible with boron, carbon, nitrogen, halogens, lead, platinum, potassium nitrate. In case of fire, use approved Class D extinguishers or smothering quantities of dry sand, crushed limestone, clay. 

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