Molybdenum bronzes

An industrial application described by Bessi6re and Martre was the use of sintered bronze/molybdenum disulphide bushes in a roller table of a system for quench-hardening heavy steel plates. The bearing experienced severe thermal cycles, and this seems the type of application for which metal composites are very appropriate. 

Typical fillers glass fiber, carbon fiber, graphite, metal powders (bronze), molybdenum sulfide, boron nitride, carbon black, Ni-Zn ferrite... 

Zinc oxide silicate Bronze Molybdenum disulfide... 

The reduction of molybdate salts in acidic solutions leads to the formation of the molybdenum blues (9). Reductants include dithionite, staimous ion, hydrazine, and ascorbate. The molybdenum blues are mixed-valence compounds where the blue color presumably arises from the intervalence Mo(V) — Mo(VI) electronic transition. These can be viewed as intermediate members of the class of mixed oxy hydroxides the end members of which are Mo(VI)02 and Mo(V)0(OH)2 [27845-91-6]. MoO and Mo(VI) solutions have been used as effective detectors of reductants because formation of the blue color can be monitored spectrophotometrically. The nonprotonic oxides of average oxidation state between V and VI are the molybdenum bronzes, known for their metallic luster and used in the formulation of bronze paints (see Paint). 

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). 

Temperature, op Carbon steel, carbon-molybdenum low-chromium (through 3 Cr Mo) 5Cr Mo through 9 Cr Mo Austenitic stainless steels, 18 Cr, 8 Ni 12 Cr 17 Cr 27 Cr 25 Cr, 20 Ni Monel 67 Ni, 30Cii 3V2 Nickel Aluminum Gray cast iron Bronze Brass 70Cii, 30 Ni Ni-Fe-Cr Ni-Cr-Fe Ductile iron... 

In cases where very high adherence is necessary an undercoating of sprayed molybdenum is applied. Owing to the volatile nature of its oxide this metal presents a clean surface to the workface and with most metals (except copper) very high adhesion is obtained. To a limited extent arc-sprayed aluminium bronze will also form a strongly adherent base coating. 

M. Greenblatt, Molybdenum oxide bronzes with quasi low-dimensional properties. Chem. Rev. 88 (1988) 31. 

J. Gabel, W. Vonau, P. Shuk, and U. Guth, New reference electrodes based on tungsten-substituted molybdenum bronzes. Solid State Ionics 169, 75-80 (2004). 

A non-enzymatic color reaction for TATP and other organic peroxides was reported recently by Apblett et al. [87, 88]. The dark blue color of molybdenum hydrogen bronze suspension is changed to yellow upon oxidation with TATP. The same reagent can also be used for quick neutralization of the sensitive explosive a lasting final blue color indicates complete neutralization. The reaction with TATP is depicted in Eq. (13). 

Colorimetric field tests for TATP and HMTD were described in Section 5 dealing with peroxide-based explosives. This group contains Keinan s PEX [85] (E. Keinan, Personal Communication, February 2006) and the kit developed by Schulte-Ladbeck et al., which involves also a preliminary stage to avoid falsepositive responses by non-explosive peroxides [86]. The color change of molybdenum hydrogen bronze suspension upon reaction with TATP was recommended also as a field test. Exposure of filter paper strips which were soaked in butanol suspension of the molybdenum compound to TATP or hydrogen peroxide vapors rapidly bleaches the blue color [87, 88]. 

Molybdenum and Tungsten Bronzes.—The results of the majority of studies of studies of new bronze phases are summarized in Table 9. Sno.2W03 and Sno.3 WO3 have been prepared and their crystal structures determined. Whether they are bronzes is debatable since they do not involve a host lattice of WO ... 

Besides magnetic perturbations and electron-lattice interactions, there are other instabilities in solids which have to be considered. For example, one-dimensional solids cannot be metallic since a periodic lattice distortion (Peierls distortion) destroys the Fermi surface in such a system. The perturbation of the electron states results in charge-density waves (CDW), involving a periodicity in electron density in phase with the lattice distortion. Blue molybdenum bronzes, K0.3M0O3, show such features (see Section 4.9 for details). In two- or three-dimensional solids, however, one observes Fermi surface nesting due to the presence of parallel Fermi surface planes perturbed by periodic lattice distortions. Certain molybdenum bronzes exhibit this behaviour. 

Adams, St., Ehses, K.-H., and Spilker, J. (1993). Proton ordering in Peierls-distorted hydrogen molybdenum bronze Hq.ssMoOs Structure and physical properties. Acta Cryst. B49, 958-67. 

Figure 3. SEM image of u sample of toroidal niesostruciured molybdenum oxide bronzes showing lack of any extended order in the structure.

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