And -iron Tungsten

Bowman, J.R. 1998. Stable-isotope systematics of skarn. In Lentz, D.R. (ed.) Mineralized intrusion-related skarn systems, 99-145. Mineralalogical Association of Canada Short Course 26. Choi, S. 1983. Skarn evolution and iron-tungsten mineralization and the associated polymetallic mineralization at the Ulsan mine, Republic of Korea. Unpublished PhD. Dissertation, Waseda University, 271 p. Choi, S., So, C., Youm, S. Kim, M. 1999. Stable isotopeand fluid inclusion studies of iron-tungsten mineralization at Ulsan skarn deposit (Abstract). Economic and Environmental Geology, 32, 148-9. 

HETEROBINUCLEAR NONACARBONYL COMPLEXES AND HYDRIDE COMPLEXES OF IRON-CHROMIUM, IRON-MOLYBDENUM, AND IRON-TUNGSTEN... 

The iron-molybdenum and iron-tungsten analogs are prepared in precisely the same manner with comparative yields of pure product. Well-formed crystals of [PPN]+ salts of the dinuclear dianion may be obtained by layering diethyl ether onto a concentrated CH3CN solution of dianion complex. 

Smo] Smoluchowski, R., Diffusion Rates of Carbon in Iron-Molybdenum and Iron-Tungsten Alloys , Phys. Rev., 63(11/12), 0438-0440 (1943) (Experimental, Phys. Prop., 7) [1944Bow] Bowman, F.E., Paike, R.M., The Partition of Molybdenum in Iron-Carbon-Molybdenum Alloys at 1300 Degrees Fahr. and the Nature of the Carbides Formed , Trans. ASM, 33, 481-493 (1944) (Experimental, Crys. Structure, 16)... 

Smo] Smoluchowski, R., Diffusion Rates of Carbon in Iron-Molybdenum and Iron-Tungsten Alloys , Phys. Rev., 63(11/12), 438-440 (1943) (Phase Relations, Experimental, Transport Phenomena, 7)... 

The BCC structure is illustrated in figure Al.3,3. Elements such as sodium, tungsten and iron fonn in the BCC structure. The conventional unit cell of the BCC structure is cubic, like FCC, with the length of the edge given by the lattice parameter, a. There are two atoms in the conventional cell. In the primitive unit cell, there is only one atom and the lattice vectors are given by... 

The first-stage catalysts for the oxidation to methacrolein are based on complex mixed metal oxides of molybdenum, bismuth, and iron, often with the addition of cobalt, nickel, antimony, tungsten, and an alkaU metal. Process optimization continues to be in the form of incremental improvements in catalyst yield and lifetime. Typically, a dilute stream, 5—10% of isobutylene tert-huty alcohol) in steam (10%) and air, is passed over the catalyst at 300—420°C. Conversion is often nearly quantitative, with selectivities to methacrolein ranging from 85% to better than 95% (114—118). Often there is accompanying selectivity to methacrylic acid of an additional 2—5%. A patent by Mitsui Toatsu Chemicals reports selectivity to methacrolein of better than 97% at conversions of 98.7% for a yield of methacrolein of nearly 96% (119). 

Ultraviolet light sources are based on the mercury vapor arc. The mercury is enclosed ia a quart2 tube and a potential is appHed to electrodes at either end of the tube. The electrodes can be of iron, tungsten, or other metals and the pressure ia a mercury vapor lamp may range from less than 0.1 to >1 MPa (<1 to >10 atm). As the mercury pressure and lamp operating temperatures are iacreased, the radiation becomes more iatense and the width of the emission lines iacreases (17). 

Cemented tungsten carbides also find use as a support for polycrystalline diamond (PCD) cutting tips, or as a matrix alloy with cobalt, nickel, copper, and iron, ia which diamond particles are embedded. These tools are employed ia a variety of iadustries including mineral exploration and development oil and gas exploration and production and concrete, asphalt, and dimension stone cutting. 

Syntheses from Dry Metals and Salts. Only metaUic nickel and iron react direcdy with CO at moderate pressure and temperatures to form metal carbonyls. A report has claimed the synthesis of Co2(CO)g in 99% yield from cobalt metal and CO at high temperatures and pressures (91,92). The CO has to be absolutely free of oxygen and carbon dioxide or the yield is drastically reduced. Two patents report the formation of carbonyls from molybdenum and tungsten metal (93,94). Ruthenium and osmium do not react with CO even under drastic conditions (95,96). 

Applications Ion implantation is widely employed to improve the life of tools. Thus press tools, dies and gear cutters can be treated to increase their durability by three times or more. Nitrogen-implanted tungsten carbide drawing dies for copper and iron wire can be improved up to fivefold. By implanting chromium, aluminium or silicon a considerable increase in the corrosion resistance of steel can be obtained. Implantation of chromium into aircraft bearing alloys has improved their durability in marine environments . 

The interstitial carbides are compounds formed by the direct reaction of a d-block metal and carbon at temperatures above 2000°C. In these compounds, the C atoms occupy the gaps between the metal atoms, as do the H atoms in metallic hydrides (see Fig. 14.9). Here, however, the C atoms pin the metal atoms together into a rigid structure, resulting in very hard substances with melting points often well above 3000°C. Tungsten carbide, WC, is used for the cutting surfaces of drills, and iron carbide, FesC, is an important component of steel. 

At 240° C mixtures of finely divided metals (aluminium, iron, tungsten) with the peroxide ignite under high friction, and molybdenum powder reacts explosively. 

Similar reactions of the ferrio-silandiols and -triols afford the ferrio-trisiloxane, 16 or the iron-/tungsten-substituted tetrasiloxanes 17a,b respectively. 

In marked contrast to the results of Gassman and Schrock, major differences were noted by Casey and co-workers in a series of studies utilizing phenylcarbene-substituted W(0) complexes in reactions with olefins. The H NMR spectra of new phenylcarbene tungsten and iron (69) complexes indicate a substantial positive charge residing on the carbene carbon, and as expected, these complexes readily form ylides on reaction with phosphines ... 

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. 

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