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Abstract
The specimen in a field-ion microscope is in the form of a fine wire,elcctropolished to a sharp point. The observed end region of the specimen is roughly hemispherical, with a radius of curvature in the range 200–1500 Å. The end region may be considered as a model of a single (small) particle of a metal powder. This can be cleaned, contaminated with various gases, oxidized, heat-treated, or coated with another metal, as desired. The resulting changes in surface morphology, the occurrence of surface reactions, and the nature of surface-transport processes can be studied at the atomic level. Examples of this approach are drawn from the authors’ work on tungsten, rhenium, iridium, and iron. The effects of oxygen, hydrogen, and carbon on these materials are described. A pronounced surface reaction when a tungsten specimen is coated with approximately one monolayer of nickel is reported. This is believed to be related to the phenomenon of the nickel-activated sintering of tungsten.
Notes
* Manuscript received 31 May 1972. Contribution to a Symposium on ‘The Role of Surface Properties in Powder Metallurgy’ to be held in Eastbourne on 20 and 21 November 1972.