Molybdenum electrodeposition

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). 

Figure 5. Overpotential of molybdenum electrodeposition onto the monocrystalline planes as a function of cathode current density.

Baraboshkin A.N. 1916) Electrocrystallization of metals from molten salt, Nauka Publishers, Moscow 2. Esina N.O., Valeev Z.I., Pankratov A. A. (1996) Structure of molybdenum electrodeposited from chloride melt with various contents of oxygen impurity in the melt. Extend Abstracts, Baltic Conference of Interface... 

MECHANISM OF THE MOLYBDENUM ELECTRODEPOSITION FROM MOLTEN SALTS... 

Comparing the results of molybdenum electrodeposition from several types of supporting electrolytes, it was found, [2] that the process is most successful in electrolytes consisting of a mixture of alkali metal fluorides and boron oxide (or alkali metal borates) to which molybdenum oxide (or alkali metal molybdate) is added as the electrochemically active component. 

Mechanical properties of tantalum boride layers 24 Mechanism of molybdenum electrodeposition 186... 

E. (2003) Influence of the bath composition and the pH on the induced cobalt-molybdenum electrodeposition. 

Gomez, E, Pellicer, E., and Valles, E. (2003) Detection and characterization of molybdenum oxides formed during the initial stages of cobalt-molybdenum electrodeposition.). AppL Electrochem., 33 (3-4), 245-252. 

Arkhipov, P.A., Baraboshkin, A.N., Valeev, Z.L, and Martem yanova, Z.S. (1990) Molybdenum electrodeposition from low-melting chloride baths (in Russian). Elektrokhimiya, 26(12), 1555-1560. 

Ruthenium is a hard, white metal and has four crystal modifications. It does not tarnish at room temperatures, but oxidizes explosively. It is attacked by halogens, hydroxides, etc. Ruthenium can be plated by electrodeposition or by thermal decomposition methods. The metal is one of the most effective hardeners for platinum and palladium, and is alloyed with these metals to make electrical contacts for severe wear resistance. A ruthenium-molybdenum alloy is said to be... 

Practices for preparation of and electroplating on Chromium (Electrodeposits) on Chromium Copper and Copper-Base Mllojs Iron Castings Eead and EeadMllojs Magnesium and Magnesium Mllojs Molybdenum and Molybdenum Mlloys MickelMlloys... 

It has been shown that the electrodeposition of molybdenum chalcogenides from high-temperature molten salts can give large, well-defined crystals of these compounds. The preparation of M0S2 as well as WS2 by electrolytic reduction of fused salts was first reported by Weiss [145], who produced small hexagonal blue-gray platelets under drastic conditions of electrolysis. Schneemeyer and Cohen... 

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... 

Chandra S, Sahu SNJ (1984) Electrodeposited semiconducting molybdenum selenide films. 1. Preparatory technique and stractural characterization. J Phys D Appl Phys 17 2115-2123 Dukstiene N, Kazancev K, Prosicevas 1, Guobiene A (2004) Electrodeposition of Mo-Se thin films from a sulfamatic electrolyte. J SoUd State Electrochem 8 330-336 Ponomarev EA, Neumann-SpaUart M, Hodes G, Levy-Qement C (1996) Electrochemical deposition of M0S2 thin films by reduction of tetrathiomolybdate. Thin SoUd EUms 280 86-89... 

Zach MP, Ng KH, Penner RM (2000) Molybdenum nanowires by electrodeposition. Science 290 2120-2123... 

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... 

Chonglun F., Piron D.L., Paradis R, Hydrogen evolution on electrodeposited nickel-cobalt-molybdenum in alkaline water electrolysis, Electrochim. Acta, 39(18), 2715-2722,1994. 

Preparation. It can be made by the irradiation of molybdenum targets with deuterium nuclei. Technetium metal may be easily prepared by reduction of NH4Tc04 (or TcC>2) with hydrogen or by electrodeposition from an NH4Tc04 solution. 

This rather useful empirical expression is applicable to many electrodeposited materials [e.g., molybdenum, zinc, steel (10)]. The expression has been able, for instance, to provide an acceptable explanation for the phenomenon of the brittle cracking in chromium electrodeposits. It has been quite helpful in the general study and understanding of the functional connection between hardness and grain size values in many electrodeposits. 

Piersma et al. demonstrated that lithium can be electrodeposited from 1-ethyl -3-methyl-imidazolium tetrachloroaluminate ionic liquid, when lithium chloride was dissolved in the melt [3], Platinum, glassy carbon and tungsten were used as working electrodes with molybdenum and platinum foils as counter electrodes. At -2.3 V a reduction peak of Li+ is observed and at about -1.6 V the stripping of lithium occurs. They noticed that the efficiency was much less than 100%. In addition, they were able to demonstrate that the addition of proton sources like triethanolamine-HCl widens the electrochemical window and allows the plating and stripping of lithium (and also sodium). 

The validity of the description of this patented procedure was also challenged on the grounds that molybdic oxide needs to be present in the plated film for the conversion to take place. It is interesting, therefore, that C E Vest introduced an important modification to the process in order to electrodeposit molybdenum trioxide instead of molybdenum metal when studying the application of the technique to the lubrication of spacecraft components. Vest s modification was to use a mixed plating bath of molybdenum trioxide in an alkali salt solution such as ammonium formate. The component being coated formed the cathode, and the molybdenum was probably present in the bath in the form of ammonium molybdate. 

Electrodeposit molybdenum trioxide from the mixed bath with a current density typicaily about 18-20 A/m, and deposition time about 3 to 10 mins., depending on the thickness required. 

The film thickness should be between 1 //m and 6 //m, and can be controlled to within 1 //m. Figure 9.1 shows the variation of final molybdenum disulphide thickness with electrodeposition time for a series of tests at 18.6A/m (12 mA/in ). 

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