Iron , single

Bare S R, Strongin D R and Somoqai G A 1986 Ammonia synthesis over iron single crystal catalysts—the effects of alumina and potassium J. Phys. Chem. 90 4726... 

Yield Stress The effect of hydrogen on the yield stress of iron and steels is unpredictable. For very pure iron single crystals and polycrystals the yield stress is frequently found to be decreased by hydrogen, but it may increase or stay the same, depending on the dislocation structure, crystal orientation and purity of the iron . Little information is available for steels. 

Figure 8.28. Ammonia rate for two types of iron single crystals (with and without promotion with potassium). [Adapted from D.R. Stongin and G.A. Somorjai,J. Catal. 109 (1988) 51.]...

TCE degradation on metallic iron single site model with competitive adsorbate // Based on adsorption equilibrium and assume that the reaction rate is directly... 

Fig. 30 Calculated partial currents / of nickel and iron, single versus alloy at 1600 rpm (from Ref. 70 with permission from the Electrochemical Society).

Dicarbonyl(i/ -cyclopentadienyl)(i -l,2,3-triphenylcyclopropen-l-yl)iron Single Procedure "... 

Iron single crystals are simulated by constructing superimposed bilayer Fe geometric clusters of N=25 and 32 to model the Fe(l 11) or the Fe(100) surface, respectively (Figure 4.1). Clusters were geometrically built up, keeping the Fe—Fe bond length constant at 0.248 nm [27],... 

Surface Science of Ammonia Synthesis Structure Sensitivity of Ammonia Synthesis Kinetics of Dissociative Nitrogen Adsorption Effects of Aluminum Oxide in Restructuring Iron Single-Crystal Surfaces for Ammonia Synthesis Characterization of the Restructured Surfaces Effect of Potassium on the Dissociative Chemisorption of Nitrogen on Iron Single-Crystal Surfaces in UHV... 

Effects of Aluminum Oxide in Restructuring Iron Single-Crystal Surfaces for Ammonia Synthesis The initial rate of ammonia synthesis has been determined over the clean Fe(l 11), Fe(lOO), and Fe(l 10) surfaces with and without aluminum oxide. The addition of aluminum oxide to the (110), (100), and (111) faces of iron decreases the rate of ammonia synthesis in direct proportion to the amount of surface covered [47]. This suggests that the promoter effect of aluminum oxide involves reaction with iron which cannot be achieved by simply depositing aluminum oxide on an iron catalyst. 

Figure 7.17. Rates of ammonia synthesis over clean iron single crystals and water-induced restructured Al,0 /Fe surfaces. Restructuring conditions are given in the figure (38J.

TPD of ammonia from iron single-crystal surfaces following high-pressure ammonia synthesis proves to be a sensitive probe of the new surface binding sites formed upon restructuring. Ammonia TPD spectra for the four clean surfaces are shown in Figure 7.19. Each surface shows distinct desorption sites. The Fe(llO) surface displays one desorption peak ( 2) with a peak maximum at 658 K. Two desorption peaks are seen for the Fe(lOO) surface 2 1 3) 556 K and 661 K. 

Effects of Potassium on Ammonia Synthesis Kinetics Extensive research has been completed in which the effects of potassium on ammonia synthesis over iron single-crystal surfaces of (111), (100), and (110) orientations [59] have been determined. The apparent order of ammonia and hydrogen for ammonia synthesis over iron and K/Fe surfaces has been determined in addition to the effect of potassium on the apparent activation energy Ef) for the reaction. In all the experiments, potassium was coadsorbed with oxygen because only about 0.15 ML of potassium coadsorbed with oxygen is stable under ammonia synthesis conditions (20... 

Effects of Potassium on the Adsorption of Ammonia on Iron Under Ammonia Synthesis Conditions The changes in the apparent reaction order dependence in ammonia partial pressure suggest that to elucidate the effects of potassium on both iron single crystals and the industrial catalyst, it is necessary to understand the readsorption of gas-phase ammonia on the catalyst surface during ammonia synthesis The fact that the rate of ammonia synthesis is negative order in ammonia synthesis. Once adsorbed, the ammonia has a certain residence time (t) on the catalyst which is determined by its adsorption energy on iron [t cx tq exp (AH /RT)]... 

N.D. Spencer, R.C. Schoonmaker, and G.A. Somorjai. Iron Single Crystals as Ammonia Synthesis Catalysts. Effect of Surface Structure on Catalyst Activity. J. Catal. lA. m (1982). 

D.R. Strongin and G.A. Somorjai. The Effects of Potassium on Ammonia Synthesis over Iron Single Crystal Surfaces. J. Catal. 109 51 (1988). 

EfTecisof Aluminum Oxide in Restructuring Iron Single-Crystal Surfaces for Ammonia Synthesis. 471... 

Hlfcci of Potassium on the Di.ssociaiivc ChcmiM)rption of Nitrogen on Iron Single-Crystal Surfaces in UHV. 475... 

SURFACE FILM EFFECTS ON DEFORMATION BEHAVIOR OF IRON SINGLE CRYSTALS AT CRYOGENIC TEMPERATURES ... 

Surface Film Effects on Deformation Behavior of Iron Single Crystals... 

Fig. 1. Stress-strain curves of control and Ni-plated iron single crystal specimens at 77 K. The tensile axis orientation is indicated in the inset.

The yield stress indicated in Fig. 3 was taken from an ultrapure iron single crystal grown from the Battelle-AISI iron [ ]. 

The authors thank T. Takeuchi of the National Research Institute for Metals, Tokyo, for providing iron single crystal sheets. Appreciation is expressed also to D. J. Quensel for reading this manuscript. 

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