On tungsten

Different types of chemisorption sites may be observed, each with a characteristic A value. Several adsorbed states appear to exist for CO chemisorbed on tungsten, as noted. These states of chemisorption probably have to do with different types of chemisorption bonding, maybe involving different types of surface sites. Much of the evidence has come initially from desorption studies, discussed immediately following. 

The electronegativity system may be used. For example, in the chemisorption (with dissociation) of hydrogen on tungsten. 

Elkowitz A B, McCreery J H and Wolken G 1976 Dynamics of atom-adsorbed atom collisions Hydrogen on tungsten Chem. Phys. 17 423... 

Todd C J and Rhodin T N 1974 Adsorption of single alkali atoms on tungsten using field emission and field desorption Surf. Sc/. 42 109-21... 

Tungsten oxytetrachlofide [13520-78-0], WOCl, mp 211°C, bp 221°(Z, is a red crystalline soHd. It is soluble in carbon disulfide and ben2ene and is decomposed to tungstic acid by water. It may be prepared by refluxing sulfurous oxychloride, SOCI2, on tungsten trioxide (12) and purified after evaporation by sublimation. 

Tungsten oxydichlofide [13520-76-8], WO2CI2, a pale-yeUow crystalline soHd having an mp of 266°C, is soluble in cold water and in alkaline solution, although partly decomposed by hot water. It is prepared by the action of carbon tetrachloride on tungsten dioxide at 250°C in a bomb (13). 

Iodides. Tungsten tetraiodide [14055-84-6] WI, is a black powder that is decomposed by air. It is prepared by the action of concentrated hydriodic acid on tungsten hexachlotide at 100°C. 

Tungsten triiodide [15513-69-6] prepared by the action of iodine on tungsten hexacarbonyl in a sealed tube at 120°C (18). 

Boron filaments are formed by the chemical vapor deposition of boron trichloride on tungsten wire. High performance reinforcing boron fibers are available from 10—20 mm in diameter. These are used mainly in epoxy resins and aluminum and titanium. Commercial uses include golf club shafts, tennis and squash racquets, and fishing rods. The primary use is in the aerospace industry. 

With CO2, compounds 70 based on tungsten and thiophene give 72. With carbon monoxide, W2(p,-CCHCHCHS)(a-2-thiophene)(NMe2)4(CO)3 results, while the 2,5-dimethylthiophene derivative gives W2(p,-CCHCHCMeS)(a-2,5-Me2C4H2S) (NMe2)4(CO)3. 

Recent results from the authors laboratory69 on the x-ray emission spectrography of tungsten or molybdenum in solution illustrate some of the points made in Section 7.13. The also show the usefulness of internal standards (7.12). Finally, the work on tungsten is closely related to the experiments on the absorption effect in sodium tungstate solutions, the results of which are summarized in Table 7-2. 

Random fluctuation of x-ray emission spectrography data on tungsten, 274-276... 

Values of X for hydrogen peaks on individual crystal planes of tungsten and molybdenum were found to be about 1-3 kcal/monolayer (101). A stronger dependence of Ed and n, resulted for nitrogen on tungsten (98). 

D.G. Barton, M. Shtein, R.D. Wilson, S.L. Soled, and E. Iglesia, Structure and Electronic Properties of Solid Acids Based on Tungsten Oxide Nanostmctures, J. Phys. Chem. 103(4), 630-640 (1999). 

Treglia G, Desjonqueres MC, Spanjaard D, LassaiUy Y, Guillot C, Jugnet Y, Due TM, Lecante J. 1981. Study of the W (Ta) cote level shifts induced hy the adsorption of oxygen on tungsten (tantalum) (110). J Phys C 14 3463-3474. 

Sawateev et al. [244] have reported on tungsten oxides with regular octahedral 6- <—Cr2WOg) and with deformed... 

There is further emphasis on adsorption isotherms, the nature of the adsorption process, with measurements of heats of adsorption providing evidence for different adsorption processes - physical adsorption and activated adsorption -and surface mobility. We see the emergence of physics-based experimental methods for the study of adsorption, with Becker at Bell Telephone Laboratories applying thermionic emission methods and work function changes for alkali metal adsorption on tungsten. 

Klein, R. The surface migration of carbon on tungsten. Physic. Rev. [2]... 

Investigation of the surface reaction of oxygen with carbon on tungsten with the field emission microscope. J. chem. Physics 21, 1177—1180 (1954). 

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