Nickel single-crystal

Beebe T P, Goodman D W, Kay B D and Yates J T Jr 1987 Kinetics of the activated dissociation adsorption of methane on low index planes of nickel single crystal surfaces J. Chem. Phys. 87 2305... 

Heiland W and Taglauer E 1973 Bombardment induced surface damage in a nickel single crystal observed by ion scattering and LEED Rad. Effects. 19 1-6... 

Figure 6.2. Stress-strain curves at a strain rate of 0.001 s T = 295 K (closed symbols), and T —11 K. (open symbols) in as-received and shock prestrained nickel-270 (polycrystalline), and in <100> and <111> nickel single crystals [11].

Worch, H., Garz, 1. and Schott, W., Influence of Surface Structure and Chemical Composition on the Pitting Corrosion of Nickel Single Crystals , Werkst. Korros., 24, 872 (1973) C.A., 80, 90185... 

We have adopted this last approach. We report here results from studies of the reaction of methyl groups on two different nickel single-crystal surfaces, Ni (100) and Ni(l 11). Nickel is... 

Low-energy electron diffraction has been used by Pitkethly and others to investigate the chemisorption of benzene, at pressures up to 10-7 Torr and at temperatures ranging from ambient to about 500°C, on the (100) (22), (110) (23,24) and (111) (22,24) faces of nickel single crystals. 

Schouten, S.C., Gijzeman, O.L., and Bootsma, G.A., Reaction of methane with nickel single crystal surfaces and the stability of surface nickel carbides, Bull. Soc. Chim. Belg., 88, 541,1979. 

A part of Figure 3 in Ref. 207, reproduced on the right, reports radial EXAFS data around the S Is absorption edge for sulfur adsorbed on the (100) plane of a g nickel single-crystal surface. The top trace corresponds to the deposition of atomic S sulfur by dehydrogenation of H2S, while g, the bottom data were obtained by adsorb- M ing thiophene on the clean surface at 100 K. Based on these data, what can be learned about the adsorption geometry of thiophene Propose a local structure for the sulfur atoms in reference to the neighboring nickel surface. 

Figure 10.1 A comparison of the rate of methane synthesis overtwo different nickel single-crystal catalysts and supported Ni/alumina catalysts at 120 torr total reactant pressure. (Reprinted from Goodman, D.W., J. Vac. Sci. Technol., 20, 522-526, 1982. With permission from the American Institute of Physics.)...

The decomposition of formic acid on nickel single crystals showed unusual features not observed on Cu(llO), Fe(lOO), Ag(110), or W(100) surfaces. Adsorption of isotopically labeled formic acid, HCCOD, or Ni(llO)... 

The nickel single crystal(MARZ grade 99.995%, supplied by MRC) was metallographically polished down to 1 pm diamond paste, then chemically polished as described by Graham and Cohen (15). Transmission x-ray diffraction measurements confirmed the (100) direction of. the face to 0,0.5°. The specimen, of area o>2 cm2, was spot-welded to a nickel rod fastened to the specimen manipulator. It could be heated by electron bombardment or radiativity and cooled to vloO K through the nickel rod and a LN -cooled copper braid. A control unit held the crystal temperature (via a chromel-alumel thermocouple spot-welded to the back of the crystal) constant to within 1 K. 

For a potential difference of 150 V, or 60,000 V we have therefore X = 1 A or 0.05 A respectively, which agrees with the experiments carried out by Davisson and Germer with nickel single crystals or by Thomson with gold foil. With the observed angles of deviation the wave length could be calculated from the lattice spacings in the same way as with X-rays. We can therefore look upon (4 ) also as the purely experimental result of these experiments from which the wave nature of the electron and the correctness of equation (4 ) appear experimentally. 

Christmann K., Schober O., ErtI G., and Neuman M., Adsorption of hydrogen on nickel single crystal surfrces, J. Phys. Chem., 60 (1974) pp.4528-4540. 

HoUoway PH, Hudson JB (1974) Kinetics of the reaction of oxygen with clean nickel single crystal surfaces 1. Ni(lOO) surface. Surf Sci 43 123... 

Chu C.-H., Hysteresis and Microstructures A Study of Biaxial Loading on Compound Twins of Copper-Aluminum-Nickel Single Crystals, PhD Thesis, University of Minnesota, 1993. (unpublished)... 

Sodium, lithium,and indium have been reported to be SERS active. In a series of papers, Krasser et 98,99,269-271 reported Raman scattering from CO and benzene adsorbed on high-surface-area Ni catalysts. Stencel and Bradley obtained, under relatively high pressures of CO, Raman spectra from nickel single crystals. The spectra were very poor, of about 10 cps. The apparent enhancement factor is unreported. Borov et al also see... 

The answer to this question can be extracted from an experiment performed by Bootsma and co-workers (ref. 2). They measured the amount of methane exposure necessary to produce a monolayer of carbon on several nickel single crystal catalysts when the methane gas was present above the catalyst at high pressures (>10"2 torr). From that measurement, they calculated a value for the probability for dissociative chemisorption of 10-9. This extremely small value for the dissociation probability immediately suggests why high pressures of methane are necessary for the observation of dissociation. Since the dissociation probability is so low, the absolute flux of incident molecules must be large in order for the dissociation rate to be high enough for carbon deposition to be observable in a reasonable amount of time. The next question is why is the dissociation probability so low ... 

That the thermal annealing of a nickel single crystal surface, for example Ni(llO) at temperatures between 1400-1700°K, does produce a change in the LEED diffraction pattern has been well documented 155,156). This additional pattern could not be removed even when the sample was heated to a temperature where there was appreciable... 

Four decades ago, Davisson and Germer (19-22) diffracted a beam of slow electrons from a (111) face of a nickel single crystal and at once revealed the great power of LEED for the study of surfaces. In their experiment the Ni(lll) diffraction pattern was altered when CO gas molecules were adsorbed into a structure having lateral periodicity... 

Thus, for both reactions a catalytic specificity of the crystal planes was found. Cunningham and Gwathmey (36) studying ethylene hydrogenation on different planes of a nickel single crystal, also arrived at the conclusion that planes cut in different crystallographic directions exhibit different activities. 

K. Christman, O. Schober, G. Ertl and M. Neumann, Adsorption of hydrogen on nickel single crystal surfaces, J. Chem. Phys., 1974, 60, 4528. 

The nickel single crystal rods were obtained from the Virginia Institute for Scientific Research, Richmond, Virginia. 

R. E. Cunningham University of Virginia) We have some experimental evidence which may support the suggestion that the orientation of the surface is more important than the actual faces exposed on facets. Wagner ) found that, within limits, deliberate roughening of the surface of a spherical nickel single crystal did not change the pattern of the carbon deposition when the crystal was heated in CO at 550°. 

Surface-science studies using nickel single-crystal surfaces revealed that the methanation reaction is surface-structure-insensitive. Both the (111) and (100) crystal faces yield the same reaction rates over a wide temperature range. These specific rates are also the same as those found for alumina-supported nickel, further proving the structure insensitivity of the process. This is also the case for the reaction over ruthenium, rhodium, molybdenum, and iron. 

Figure 2. The selective deposition of carbon on the (111) faces of a nickel single crystal during the catalytic decomposition of carbon monoxide at 550 C. (Reproduced from Ref.11. Copyright 1948, American Chemical Society.)...

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