Cobalt-uranium oxides

Carbide-based cermets have particles of carbides of tungsten, chromium, and titanium. Tungsten carbide in a cobalt matrix is used in machine parts requiring very high hardness such as wire-drawing dies, valves, etc. Chromium carbide in a cobalt matrix has high corrosion and abrasion resistance it also has a coefficient of thermal expansion close to that of steel, so is well-suited for use in valves. Titanium carbide in either a nickel or a cobalt matrix is often used in high-temperature applications such as turbine parts. Cermets are also used as nuclear reactor fuel elements and control rods. Fuel elements can be uranium oxide particles in stainless steel ceramic, whereas boron carbide in stainless steel is used for control rods. 

Oxides.—Amongst the simple oxides may be classed —oxide of chromium, oxide of iron, oxide of uranium, oxide of manganese, oxide of zinc, oxide of cobalt, oxide of antimony, oxide of copper, oxide of tin. 

More and more minerals are being found amenable to bacteriological leaching. The copper sulfide minerals, such as chalcopyrite (B31-B33, D22, D24), chalcocite (B35), and tetrahedrite (B32, D21) are among the best studied. The iron sulfide (pyrite) (B31, B33, C22, L4) and sulfur (B33, B34, C22, L4) oxidation processes are the best understood. Investigations on the leaching of nickel sulfides (D21, D24, T17), lead sulfide (E4), molybdenum sulfide (molybdenite) (B17, B31, D24), cobalt sulfide (D9), zinc sulfide (D24), and uranium oxide (D24, F2, H13, H14, Ml) have been reported in the literature. 

T1 ecent investigations have shown that chromium, manganese, cobalt, nickel, copper, and zinc oxides react with uranium oxides at elevated temperatures to form double oxides with the formulas MUO4 and MU3O10. Table I lists eight compounds for which some structural and thermal stability information has been reported. 

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. 

The uranium oxide data in Table 7.8 were collected on a Teledyne Leeman Labs Prodigy DC Arc. The uranium oxide was mixed with a small amount of gallium oxide/cobalt oxide buffer and 125 mg of the buffered sample were analyzed. The prebum time was 4 s, and the elements were determined in a 4-45 s integration time. The details are available in an application note available from Teledyne Leeman Labs, along with other examples of the use of DC arc emission for materials analysis. 

Surprisingly, uranium oxide has been shown to be highly active for the deep oxidation of several VOCs7 It showed moderate conversion for propane and butane oxidation and only a low activity for methane and ethaneJ Inversely to the situation observed with cobalt oxide, when U3 Og was supported on silicathe activity increased compared with the bulk oxide. Supporting the uranium oxide resulted in modification of the structure and chemistry of the oxide leading to an increase in the defective structure, which resulted in an increased oxidation activity. 

Catalysts used for preparing amines from alcohols iaclude cobalt promoted with tirconium, lanthanum, cerium, or uranium (52) the metals and oxides of nickel, cobalt, and/or copper (53,54,56,60,61) metal oxides of antimony, tin, and manganese on alumina support (55) copper, nickel, and a metal belonging to the platinum group 8—10 (57) copper formate (58) nickel promoted with chromium and/or iron on alumina support (53,59) and cobalt, copper, and either iron, 2iac, or zirconium (62). 

Cathodic stripping voltammetry has been used [807] to determine lead, cadmium, copper, zinc, uranium, vanadium, molybdenum, nickel, and cobalt in water, with great sensitivity and specificity, allowing study of metal specia-tion directly in the unaltered sample. The technique used preconcentration of the metal at a higher oxidation state by adsorption of certain surface-active complexes, after which its concentration was determined by reduction. The reaction mechanisms, effect of variation of the adsorption potential, maximal adsorption capacity of the hanging mercury drop electrode, and possible interferences are discussed. 

CSC atomization was developed by AEA Harwell Laboratories in the UK in the early 1970 s. Initially, the CSC process was used for the atomization of refractory and oxide materials such as alumina, plutonium oxides, and uranium monocarbide in nuclear fuel applications. Since it is well-suited to the atomization of reactive metals/alloys or those subject to segregation, the CSC process has been applied to a variety of materials such as iron, cobalt, nickel, and titanium alloys and many refractory metals. The process also has potential to scale up to a continuous process. 

Malinin, G. V. et al., Russ. Chem. Rev., 1975, 44, 392-397 Thermal decomposition of metal oxides was reviewed. Some oxides (cobalt(II, III) oxide, copper(II) oxide, lead(II, IV) oxide, uranium dioxide, triuranium octaoxide) liberate quite a high proportion of atomic oxygen, with a correspondingly higher potential for oxidation of fuels than molecular oxygen. 

Metals are extremely important not only for chemical reactions but also for the health and welfare of plants and animals. Some examples of metals required for good nutrition, even in trace amounts, are iron, copper, cobalt, potassium, sodium, and zinc. Other metals—for example, mercury, lead, cadmium, barium, beryllium, radium, and uranium—are very toxic. Some metals at the atomic and ionic levels are crucial for the oxidation process that metabolizes carbohydrates for all living cells. 

Depending on type, uranium deposits exhibit characteristic primary alteration and trace element zoning patterns, the latter commonly including, but are not limited to, elements exhibiting changes in oxidation state such as vanadium, selenium, molybdenum, arsenic, cobalt, and nickel (Fig. 3). It can be shown that... 

Molybdenum In its pure form, without additions, it is the most efficient catalyst of all the easily obtainable and reducible substances, and it is less easily poisoned than iron. It catalyzes in another way than iron, insofar as it forms analytically easily detectable amounts of metal nitrides (about 9% nitrogen content) during its catalytic action, whereas iron does not form, under synthesis conditions, analytically detectable quantities of a nitride. In this respect, molybdenum resembles tungsten, manganese and uranium which all form nitrides during their operation, as ammonia catalysts. Molybdenum is clearly promoted by nickel, cobalt and iron, but not by oxides such as alumina. Alkali metals can act favorably on molybdenum, but oxides of the alkali metals are harmful. Efficiency, as pure molybdenum, 1.5%, promoted up to 4% ammonia. 

Of the important properties of glass, color is one of the most interesting. Color is usually achieved by the addition of various metal oxides. The strongest of these are titanium, vanadium, chromium, manganese, selenium, iron, cobalt, nickel and copper. Silver and uranium will give weak colors. Some of the rare earths are also used as colorants with sharp absorption bands in contrast to the broad bands given by most colorants. (4)... 

Shortly after the introduction of the bismuth molybdate catalysts, SOHIO developed and commercialized an even more selective catalyst, the uranium antimonate system (4). At about the same time, Distillers Company, Ltd. developed an oxidation catalyst which was a combination of tin and antimony oxides (5). These earlier catalyst systems have essentially been replaced on a commercial scale by multicomponent catalysts which were introduced in 1970 by SOHIO. As their name implies, these catalysts contain a number of elements, the most commonly reported being nickel, cobalt, iron, bismuth, molybdenum, potassium, manganese, and silica (6-8). 

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