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Molybdenum cathode

Fused salts Molybdenum has excellent resistance to a wide range of fused salts and has been used in the fused salt electrolysis of magnesium, platinum, thorium and uranium. In the production of pure magnesium, molybdenum is used to couple graphite electrodes electrically. Molybdenum cathodes are... [Pg.846]

The electrolyte is made by in situ chlorination of vanadium to vanadium dichloride in a molten salt bath. Higher valent chlorides are difficult to retain in the bath and thus are not preferred. The molten bath, which is formed by sodium chloride or an equimolar mixture of potassium chloride-sodium chloride or of potassium chloride-lithium chloride or of sodium chloride-calcium chloride, is contained in a graphite crucible. The crucible also serves as an anode. Electrolysis is conducted at a temperature about 50 °C above the melting point of the salt bath, using an iron or a molybdenum cathode and a cathode current density of 25 to 75 A dnT2. The overall electrochemical deposition reaction involves the formation and the discharge of the divalent ionic species, V2+ ... [Pg.720]

In the electrolytic process, a fused bath of yttrium fluoride and lithium fluoride is heated to nearly 1,700°C and electrolyzed. The electrolysis is done in a graphite crucible using molybdenum cathodes at which yttrium is produced as molten metal. [Pg.978]

Electrocatalytic possibilities with C02 reduction in aqueous solution are surprising. On copper at 0 °C, CH4 is the main product from electrolysis, and on a molybdenum cathode at room temperature, it is methanol (Hori, 1980). Using lead in a porous gas diffusive electrode, it has been possible to obtain HCOOH at 100 mA cm-2 (Hallmann, 1991). Macrocyclic compounds catalyze the reduction of C02 to CO to... [Pg.500]

Two other ways are available for obtaining metallic uranium (i) by the electrolysis of KUFg in fused CaClg (80%) and NaCl (20%) at 900° with the graphite container as anode and a molybdenum cathode. The current density employed is 1.5 amp/cm and the product better than 99.9%. (ii) by the hot-wire technique (Van Arkel and De Boer, 1925), also used for Ti (p. 449), Zr and W, applied to UI4. [Pg.435]

However, Hori (1986) found the electrocatalytic reduction of carbon dioxide to methane on a molybdenum cathode to be electrocatalytic [11]. One hundred percent reduction of carbon dioxide to methanol at 0°C was reported. What remains open to research is the use of nonaqueous solvents, for example, acetonitrile, because there would be then no competition from hydrogen evolution. Carbon dioxide does undergo electrochemical reduction in acetonitrite to glycolic acid. Here is a research topic, which could have world consequences and cost very little (about 105 per year per researcher, even a dozen would make a great difference in five years). [Pg.35]

Electrolysis of fused salts. The first electrolytic processes used thorium fluorides, as these are less hygroscopic than thorium chloride. In a process developed for the U.S. AEC fS3], a solution of dried 15 to 20% KThFs in molten sodium chloride was electrolyzed at 800 to 900°C in a graphite anodic cell with a molybdenum cathode under an inert argon atmosphere. As only chlorine was produced at the anode, fluorides accumulated in the electrolyte and required its periodic renewal. A somewhat similar process, involving electrolysis of Thp4 in molten KCl/NaCl has been used in the Soviet Union [Kl]. [Pg.311]

The cathodes can be of the hot type such as tungsten, carbon or molybdenum, cathodes which obviously must be used in a non oxidizing atmosphere. Under certain conditions of oxidizing atmosphere one can use zirconium or hafnium cathodes. The so-called cold cathodes are generally made of copper is -i - ). Heat losses at the cathode are generally quite low (less than 15% of power input to the arc). For a tungsten cathode tip, erosion with current is of g/Clb... [Pg.121]

In operation, a pre-electrolysis is carried out in a new cell, under normal operating conditions, for several days, to remove moisture and other impurities. A new molybdenum cathode is then inserted for the main electrolysis. The final cathode deposit is crushed and leached with water before washing in alcohol and ether, and vacuum drying. Any surface film of oxide may be removed during the leaching operations, if one of the water leaches is replaced by dilute acid. [Pg.286]

A molybdenum cathode was employed with a graphite crucible as the anode and the electrolysis temperature was about 800°C. After a standard leaching operation with water, nitric acid, water again, and alcohol for drying, the finer particles often had too high a surface oxide content for compaction. The coarser particles only therefore were separated off for use. ... [Pg.289]

The electrode system can take several forms. In one of these a suspended graphite rod sheathed in Mullite is used as the cathode support, the electrode itself consisting of a small horizontal molybdenum disc fixed to the lower end, which in operation is located two or three inches above the ceU base. The anode is a graphite annulus suspended from two graphite rods, a few inches above the molybdenum cathode. A molybdenum catch-plate rests on the base of the cell to collect thorium metal particles which fall from the cathode. This can be raised from the ceU and drained in the same way as the cathode itself, by removal of the ceU Ud. [Pg.291]

A very pure grade of thorium metal can be produced in small quantities by fused salt electrolysis in a refining cell. Thorium tetrachloride or tetra-fiuoride is added to twice its weight of a lithium chloride, potassium choride eutectic (m.p. 3S2°C) and electrolysed between an anode of impure thorium metal and a molybdenum cathode, at a temperature of 400-50°C (forThF4), or 600-50°C (For ThCU). A tubular-shaped container of fused silica is employed. [Pg.293]

Waves Rj and Ox correspond to the discharge of alkali metal cations at the molybdenum cathode and the dissolution of alkali metals, respectively. Shoulder OX4 on the voltammograms arises from the oxidation of oxide ions at a molybdenum surface, as it was confirmed by addition of Li20 to the melt. [Pg.333]

Only about 10 elements, ie, Cr, Ni, Zn, Sn, In, Ag, Cd, Au, Pb, and Rh, are commercially deposited from aqueous solutions, though alloy deposition such as Cu—Zn (brass), Cu—Sn (bronze), Pb—Sn (solder), Au—Co, Sn—Ni, and Ni—Fe (permalloy) raise this number somewhat. In addition, 10—15 other elements are electrodeposited ia small-scale specialty appHcations. Typically, electrodeposited materials are crystalline, but amorphous metal alloys may also be deposited. One such amorphous alloy is Ni—Cr—P. In some cases, chemical compounds can be electrodeposited at the cathode. For example, black chrome and black molybdenum electrodeposits, both metal oxide particles ia a metallic matrix, are used for decorative purposes and as selective solar thermal absorbers (19). [Pg.528]

In all cases partial or total hulls of aluminum or stainless steel must be provided with cathodic protection. This also applies to high-alloy steels with over 20% chromium and 3% molybdenum since they are prone to crevice corrosion underneath the coatings. The design of cathodic protection must involve the particular conditions and is not gone into further here. [Pg.397]

Edwards e/a/. carried out controlled potential, slow strain-rate tests on Zimaloy (a cobalt-chromium-molybdenum implant alloy) in Ringer s solution at 37°C and showed that hydrogen absorption may degrade the mechanical properties of the alloy. Potentials were controlled so that the tensile sample was either cathodic or anodic with respect to the metal s free corrosion potential. Hydrogen was generated on the sample surface when the specimen was cathodic, and dissolution of the sample was encouraged when the sample was anodic. The results of these controlled potential tests showed no susceptibility of this alloy to SCC at anodic potentials. [Pg.476]

The theoretical aspects of molybdenum s corrosion behaviour are complex and there is as yet no clear cut, generally applicable picture. There are, however, a large number of literature references which include data on polarisation, passivation and potential of molybdenum under widely assorted conditions. The electrode potential of molybdenum depends on its surface condition. For example, some tests showed an of -t-0-66V when the molybdenum was passivated by treatment with concentrated chromic acid and —0-74 V after activation by cathodic treatment in sodium hydroxide. [Pg.841]

On account of the fact that the electrode potential of molybdenum is more negative than the discharge potential of hydrogen, principle difficulties arise to cathodically electrodeposit molybdenum chalcogenide films from aqueous solutions. Theoretically, the deposition of pure molybdenum by electrolytic reduction of molybdates in acidic aqueous solutions is possible according to the reaction... [Pg.110]

Mild Y, Nakazato D, Ikuta H, Uchida T, Wakihara M (1995) Amorphous M0S2 as the cathode of Uthium secondary batteries. J Power Sources 54 508-510 Yufit V, Nathan M, Golodnitsky D, Peled E (2003) Thin-fihn Uthium and Uthium-ion batteries with electrochemicaUy deposited molybdenum oxysulfide cathodes. J Power Sources 122 169-173... [Pg.146]

Shembel EM, Apostolova RD, Tysyachnyi VP, Kirsanova IV (2005) Thin-layer electrolytic molybdenum oxydisulfides for cathodes of Lithium batteries. Russ J Electrochem 41 1305-1315... [Pg.346]

In the case of molten salts, the functional electrolytes are generally oxides or halides. As examples of the use of oxides, mention may be made of the electrowinning processes for aluminum, tantalum, molybdenum, tungsten, and some of the rare earth metals. The appropriate oxides, dissolved in halide melts, act as the sources of the respective metals intended to be deposited cathodically. Halides are used as functional electrolytes for almost all other metals. In principle, all halides can be used, but in practice only fluorides and chlorides are used. Bromides and iodides are thermally unstable and are relatively expensive. Fluorides are ideally suited because of their stability and low volatility, their drawbacks pertain to the difficulty in obtaining them in forms free from oxygenated ions, and to their poor solubility in water. It is a truism that aqueous solubility makes the post-electrolysis separation of the electrodeposit from the electrolyte easy because the electrolyte can be leached away. The drawback associated with fluorides due to their poor solubility can, to a large extent, be overcome by using double fluorides instead of simple fluorides. Chlorides are widely used in electrodeposition because they are readily available in a pure form and... [Pg.697]

The deposition of molybdenum occurs due to the discharge of the anionic species at the cathode and thus depends on the concentration and the diffusion of this species in the... [Pg.722]

These chemical reactions possibly precede the electrochemical reactions. Thus the electrochemical reactions in the case of molybdenum oxides may be taken to be similar to those which occur in electrorefining, i.e., electrochemical dissolution of molybdenum from the impure metallic molybdenum anode and subsequent deposition at the cathode. The combination of the chemical and the electrochemical reactions occurring at the anode can be represented in the following way ... [Pg.722]

Field emission displays are VFDs that use field emission cathodes as the electron source. The cathodes can be molybdenum microtips,33-35 carbon films,36,37 carbon nanotubes,38" 16 diamond tips,47 or other nanoscale-emitting materials.48 Niobium silicide applied as a protective layer on silicon tip field emission arrays has been claimed to improve the emission efficiency and stability.49 ZnO Zn is used in monochrome field emission device (FED) displays but its disadvantage is that it saturates at over 200 V.29... [Pg.696]


See other pages where Molybdenum cathode is mentioned: [Pg.721]    [Pg.1051]    [Pg.39]    [Pg.1051]    [Pg.282]    [Pg.285]    [Pg.4198]    [Pg.163]    [Pg.721]    [Pg.1051]    [Pg.39]    [Pg.1051]    [Pg.282]    [Pg.285]    [Pg.4198]    [Pg.163]    [Pg.1378]    [Pg.502]    [Pg.136]    [Pg.532]    [Pg.900]    [Pg.907]    [Pg.1215]    [Pg.624]    [Pg.110]    [Pg.111]    [Pg.244]    [Pg.327]    [Pg.328]    [Pg.329]    [Pg.215]    [Pg.525]   
See also in sourсe #XX -- [ Pg.15 , Pg.15 , Pg.28 , Pg.149 , Pg.246 , Pg.277 , Pg.282 , Pg.285 ]




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