Atomic-Level Modulation of the Interface Chemistry of Platinum–Nickel Oxide toward Enhanced Hydrogen Electrocatalysis Kinetics

There is considerable technological interest in oxidation of nickel because of the importance of nickel-base superalloys in high-temperature oxidizing environments. NiO scales on nickel grow classically, by outward diffusion of nickel through the scale, and are among the most studied of oxidation systems. We report here the first extensive characterization by transmission electron microscopy of nickel oxide scales formed on bulk nickel substrates and sectioned both parallel and transversely to the Ni/NiO interface.Electrochemically-polished nickel sheet of 99.995% purity was oxidized at 1273 K in 0.1 MPa oxygen partial pressure for times between 5 s and 25 h. Parallel sections were produced using a combination of electropolishing of the nickel substrate and ion-beam thinning of the scale to any desired depth in the scale. Transverse sections were prepared by encasing stacked strips of oxidized nickel sheet in epoxy resin, sectioning transversely and ion-beam thinning until thin area spanning one or more interfaces was obtained.

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Atomic-level imaging of the surface structure of Ag2O

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100113160 ◽

1984 ◽

Vol 42 ◽

pp. 656-657

Author(s):

William Krakow

Keyword(s):

High Vacuum ◽

Atomic Level ◽

Ultra High Vacuum ◽

Research Groups ◽

Resolution Electron ◽

Surface Reconstructions ◽

Order Of Magnitude ◽

High Resolution Electron Microscope ◽

Saturated Structure ◽

Transmission And Reflection

In recent years electron microscopy has been used to image surfaces in both the transmission and reflection modes by many research groups. Some of this work has been performed under ultra high vacuum conditions (UHV) and apparent surface reconstructions observed. The level of resolution generally has been at least an order of magnitude worse than is necessary to visualize atoms directly and therefore the detailed atomic rearrangements of the surface are not known. The present author has achieved atomic level resolution under normal vacuum conditions of various Au surfaces. Unfortunately these samples were exposed to atmosphere and could not be cleaned in a standard high resolution electron microscope. The result obtained surfaces which were impurity stabilized and reveal the bulk lattice (1x1) type surface structures also encountered by other surface physics techniques under impure or overlayer contaminant conditions. It was therefore decided to study a system where exposure to air was unimportant by using a oxygen saturated structure, Ag2O, and seeking to find surface reconstructions, which will now be described.

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HREM observation of NiO growth on submicron spheres of pure nickel

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100154718 ◽

1989 ◽

Vol 47 ◽

pp. 548-549

Author(s):

C.M. Teng ◽

T.F. Kelly ◽

J.P. Zhang ◽

H.M. Lin ◽

Y.W. Kim

Keyword(s):

Nickel Oxide ◽

Grain Boundaries ◽

Pure Nickel ◽

Submicron Particles ◽

Crystal Formation ◽

Nickel Wire ◽

Liquid Droplets ◽

Oxide Interface ◽

Nickel Chromium ◽

Chromium Alloys

Spherical submicron particles of materials produced by electrohydrodynamic (EHD) atomization have been used to study a variety of materials processes including nucleation of alternative crystallization phases in iron-nickel and nickel-chromium alloys, amorphous solidification in submicron droplets of pure metals, and quasi-crystal formation in nickel-chromium alloys. Some experiments on pure nickel, nickel oxide single crystals, the nickel/nickel(II) oxide interface, and grain boundaries in nickel monoxide have been performed by STEM. For these latter studies, HREM is the most direct approach to obtain particle crystal structures at the atomic level. Grain boundaries in nickel oxide have also been investigated by HREM. In this paper, we present preliminary results of HREM observations of NiO growth on submicron spheres of pure nickel.Small particles of pure nickel were prepared by EHD atomization. For the study of pure nickel, 0.5 mm diameter pure nickel wire (99.9975%) is sprayed directly in the EHD process. The liquid droplets solidify in free-flight through a vacuum chamber operated at about 10-7 torr.

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Surface roughness measurements of vanadium-contaminated fluidized cracking catalysts by atomic force microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100166798 ◽

1996 ◽

Vol 54 ◽

pp. 866-867

Author(s):

H. Kinney ◽

M.L. Occelli ◽

S.A.C. Gould

Keyword(s):

Surface Roughness ◽

Zeolite Y ◽

Atomic Level ◽

Microporous Structure ◽

Contact Mode ◽

Force Microscopy ◽

Atomic Force ◽

Before And After ◽

Roughness Measurements ◽

Cracking Catalysts

For this study we have used a contact mode atomic force microscope (AFM) to study to topography of fluidized cracking catalysts (FCC), before and after contamination with 5% vanadium. We selected the AFM because of its ability to well characterize the surface roughness of materials down to the atomic level. It is believed that the cracking in the FCCs occurs mainly on the catalysts top 10-15 μm suggesting that the surface corrugation could play a key role in the FCCs microactivity properties. To test this hypothesis, we chose vanadium as a contaminate because this metal is capable of irreversibly destroying the FCC crystallinity as well as it microporous structure. In addition, we wanted to examine the extent to which steaming affects the vanadium contaminated FCC. Using the AFM, we measured the surface roughness of FCCs, before and after contamination and after steaming.We obtained our FCC (GRZ-1) from Davison. The FCC is generated so that it contains and estimated 35% rare earth exchaged zeolite Y, 50% kaolin and 15% binder.

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