Molybdenum, polycrystalline

The 3 mm disc was covered by a 3 pm thick polycrystalline nickel foil, then a polycrystalline molybdenum disc was placed on top of the nickel foil. This composite sandwich was placed between two alumina supports and heated for 30 min at 1350°C. The cross-sections used for microanalysis were prepared by cutting with a wire saw in a direction perpendicular to the grain boundary, then mechanically and chemically polished. 

Non-noble metal molybdenum containing carbonyls were studied for ORR activity.189-191 Mox(CO) and Mo,Sr(C 0) were studied side by side.189 190 These high-nuclearity carbonyl compounds were prepared by sintering. It was found that the Mox(CO) was amorphous by XRD, however, as S was added, a polycrystalline/ amorphous combination was formed in the catalyst. While neither Mox(CO) or Mo SyCO), compounds were found to be very active for ORR, the addition of S to Mox(CO) appeared to nullify any activity towards ORR.189 190 MoxSeJ,(CO) was produced by both screen printing and sintering191 as well as chemical synthesis.192 The screen printed catalysts were more active than the sintered catalysts, but as the amount of Se increased, the ORR activity decreased.191 192... 

Fig. 10.3 Colour contrast of human erythrocytes on different solid reflective substrates Al -polycrystalline aluminum Cu - polycrystalline copper Mo - monocrystalline molybdenum Ni - polycrystalline nickel Pt - chemically polished platinum Si(m) - monocrystalline silicon Si(p) - polycrystalline silicon Ti - chemically polished titanium W- monocrystalline tungsten...

The best colour contrast of red blood cells is achieved on mono- and polycrystalline silicon, and monocrystalline surfaces of refractory metals molybdenum and tungsten, which possess maximal reflectivity. 

Boudart et al.20 studied nitrogen adsorption and ammonia decomposition on polycrystalline molybdenum and reported that the surface was predominantly covered with adsorbed N and some dissociated species such as NH2. N2 formation was thought to proceed through the recombination of adsorbed nitrogen on the surface above 645 K.22. Haddix et al.23 have reported that decomposition of NH3 adsorbed on y-Mo2N produces... 

The molybdenum(IV) oxide crystals produced by this method are thick, oblong needles or thick platelets having a brown-violet metallic luster. The cell edges are close to those reported for the polycrystalline powders,7 monoclinic crystals with a = 5.60 A., b = 4.86 A., c = 5.63 A., 0 = 120.95°. The crystals are excellent metallic conductors. 

A schematic representation of the apparatus [21] is shown in Fig. 2. An electrostatically focused beam (105 e+/s at 65 eV) enters a section of waveguide (2.3cm x 1.0cm) and strikes a polycrystalline molybdenum target attached to the opposite inner wall... 

Srivastava, S.K., Avasthi, B.N., Das, B. and Basu, S., High-Pressure Growth of Polycrystalline Molybdenum Disulphide, Materials Letters, 1, 178, (1983). 

EXAFS data from frozen solutions and polycrystalline samples can provide information about the number, type, and distances of atoms coordinated to the molybdenum atom, but not angular information that defines stereochemistry. Mo L-edge spectroscopy has been used to investigate the 2p 4d electronic transitions of the molybdenum atom in sulfite oxidase and model compounds in order to obtain information about the symmetry and electronic structure of the molybdenum center (70). 

SEM/KUL] Semenov-Kobzar, A. A., Kulikov, L. M., Bogatyr, A. S., Zaletilo, L. S., Thermal stability of polycrystalline molybdenum and tungsten diselenides in argon, Inorg. Mater., 28, (1992), 693-695. Cited on pages 345, 348, 573. 

The nanohardness of 400 nm thickness chromium coatings with ultra-fine grain (nanocrystalline) structure is equal to 21.61 GPa (Table 1), which is 8-9 times higher than that of cast chromium. At the same time the nanohardness of molybdenum coatings, which characterized even more fine-grain structure, is equivalent to 9.98 GPa. It is necessary to note, that in a massive state hardness of polycrystalline chromium is lower than hardness of polycrystalline molybdenum (2 GPa and 1.3 GPa for poly crystalline molybdenum and chromium accordingly [7]). 

The close similarity between adsorption of CO on tungsten and molybdenum is shown by the work of Jackson and Hooker (82) in a LEED study on the Mo(llO) face when they observed a complex ordered structure formed by heating the crystal to 1300°K in the presence of CO. This surface structure shows a marked resemblance to that obtained by May and Germer on W(llO) (71) after annealing the crystal to between 600-900°K. On molybdenum the removal of the additional structure was not observed until about 1800°K, whereas on W(llO) CO was observed to desorb at 1100°K. This result is puzzling in the light of the flash filament studies and calorimetric heats of adsorption on polycrystalline samples which indicate a weaker adsorption process for CO on poly crystalline molybdenum compared with tungsten. 

This tracer study also suggested a low sticking probability in the range 10 -10 for CO on molybdenum at room temperature, a result comparable with other studies on polycrystalline molybdenum samples using various techniques (86). The results of Roberts (55) for the... 

The Radioactive Tracer Results of Crowell and Matthews on Polycrystalline Molybdenum... 

A variety of polycrystalline substrates have been employed during CVD growth, including silicon and self-passivating metals such as niobium, molybdenum,... 

Beryllium Oxide (BeO) — polycrystalline Molybdenum Disilicide (MoSi2) Spinel (AI2O3 MgO) Dichromium Trioxide (Cr203) 8.4 8.5 X10 for 25-800X 8.41x10 for 0-1000"C 8.41x10 for 25 to 1000"C 8.43x10 for 25-500 C... 

Aluminum Oxide (AI2O3) — polycrystalline Aluminum Oxide (AI2O3) — polycrystalline Beryllium Oxide (BeO) perpendicular to c axis Molybdenum Disilicide (MoSi2) 8.45 x 10 for 0 to 1427"C 8.49xl0 for0tol527 C 8.5x 10 for 28to749 C 8.51 X 10- for 25-1000 C... 

Molybdenum Disilicide (MoSi2) Aluminum Oxide (AI2O3) — polycrystalline Dichromium Trioxide (Cr203) Thorium Dioxide (Th02) 8.56x10 for 0-1400°C 8.58x10 for 0 to 1727"C 8.62 x 10 for 25-1000"C 8.63x10 for 25 to 500 C... 

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