Preparation uranium oxides

FIGURE 5.17 The chromatogram of a laboratory prepared uranium oxide sample showing the intensity of the Th and U signals as a function of time, recorded at medium resolution (R = 4000) of the ICP-SF-MS. (From Varga, Z. and Suranyi, G., Anal. Chim. Acta, 599, 16, 2007. With permission.)... 

Uranium can be prepared by reducing uranium halides with alkali or alkaline earth metals or by reducing uranium oxides by calcium, aluminum, or carbon at high temperatures. The metal can also be produced by electrolysis of KUF5 or UF4, dissolved in a molten mixture of CaCl2 and NaCl. High-purity uranium can be prepared by the thermal decomposition of uranium halides on a hot filament. 

Preparation of Uranium Metal. Uranium is a highly electropositive element, and extremely difficult to reduce. As such, elemental uranium caimot be prepared by reduction with hydrogen. Instead, uranium metal must be prepared using a number of rather forcing conditions. Uranium metal can be prepared by reduction of uranium oxides (UO2 [1344-59-8] or UO [1344-58-7] with strongly electropositive elements (Ca, Mg, Na), reduction of uranium halides (UCl [10025-93-1], UCl [10026-10-5] UF [10049-14-6] with electropositive metals (Li, Na, Mg, Ca, Ba), electro deposition from molten... 

Uranium oxides are of importance in the nuclear industry, and for this reason considerable effort has been put into understanding their nonstoichiometric behavior. The dioxide, U02 crystallizes with the fluorite structure with an ideal composition MX2 (Fig. 4.7a) but is readily prepared in an oxygen-rich form. In this state it is... 

Uranium is best known as a fuel for nuclear power plants. To prepare this fuel, uranium ores are processed to extract and enrich the uranium. The process begins by mining uranium-rich ores and then crushing the rock. The ore is mixed with water and thickened to form a slurry. The slurry is treated with sulfuric acid and the product reacted with amines in a series of reactions to give ammonium diuranate, (NH4)2U20 . Ammonium diuranate is heated to yield an enriched uranium oxide solid known as yellow cake. Yellow cake contains from 70—90% U3Og in the form of a mixture of U02 and U03. The yellow cake is then shipped to a conversion plant where it can be enriched. 

What other uranium oxide is known How is it prepared ... 

U(OEt)5 is easily prepared by oxidation of U(OEt)4 by bromine in ethanol, followed by addition of the calculated quantity of sodium ethoxide, a reaction which yields181 only Np(OEt)4Br in the case of Np(OEt)4. U(OEt)s is commonly used as the starting material for the preparation of other uranium(V) alkoxides by alcohol exchange reactions. A comprehensive review of metal alkoxides includes a useful discussion of the uranium(V) compounds.182... 

Experimental. Uranium oxide electrodes were prepared from sintered UC>2 and reduced to the correct stoichiometry in a vacuum furnace. After cleaning, samples were exposed to a 0.5 M Na2S0 solution of pH 7 and electrochemically oxidized at a potential of +300 mVgcg. After various times, samples were removed from the solution within the inert gas chamber. They were rinsed in deoxy-genated water and transferred into the UHV chamber within 60 seconds. XPS peaks were taken using an Al Ka X-ray source. 

Thorium oxide fluoride (Th2OF5) (277) has been prepared from ThF4 and ThOF, and the reaction of uranium oxides with UF4 at 400-500°C is said to produce U205F as one of the products (278). 

Although there are a number of reported methods for preparing uranium hexachloride, most of them can be grouped under two types.(1) Uranium hexachloride can be prepared by further chlorination of lower uranium chlorides. This type includes those preparations in which a uranium oxide is the starting material, since a lower uranium chloride is normally formed as an intermediate in these chlorination reactions. (2) Uranium hexachloride is formed in the thermal decomposition of uranium pentachloride. Neither method yields uranium hexachloride in a very pure form. Uranium/chlorine ratios of 1 5.8 to 5.9 are normally the best encountered. 

Among the transition metals from chromium through zinc, iron remains the only element for which no double oxide formation with uranium oxide has been reported. Both the l.T and 1 3 compounds of mainganese, cobalt, and copper have been prepared, while only the 1 1 compound of chromium, and the 1 3 compound of nickel and zinc are known. 

Preparation of Uranyl Metaborate. An anhydrous boric oxide glass is prepared by thermal decomposition of boric acid in a platinum dish. The uranium oxide powder is then spread on the surface of the boric oxide, and the reactants are heated in air at — 1000°C. until Reaction 1... 

Bradley reported that homoleptic uranium hexakis(alkoxide) complexes coordinated by secondary and tertiary alkoxides (U(OR)6 R = Pr , Bu , Bu ) were produced from thermal disproportionation of U0(0R)4 vide suprd) U(OMe)6 was initially prepared from oxidation of U (OMe)5 in the presence of benzoyl peroxide. Interest in a more convenient synthetic route to U(OMe)6 was stimulated by its potential use in uranium isotope separation, which can be achieved with a CO2 laser. Facile syntheses of U(OMe)6 were reported by different groups (see Equations (48) to (51)) ... 

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