Nature and origin of particles in condensation fume: a review*

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Abstract
SUMMARY: Precipitate from the fume generated in steelmaking contains chiefly iron in the form of metallic and oxide particles. Significant amounts of zinc and lead may also be present when, as in the U.K., there is substantial recycling of ferrous scrap. Conflicting explanations have been suggested for the sudden release of oxide (‘brown fume’) to form airborne aggregates of ultramicroscopic particles. The presence of free metal, usually as spheres of much larger size than those of the oxide, is attributed to the condensation of vapour to droplets which somehow escape oxidation.Recently, several studies have been reported on the particles in smokes generated by heating metals in an inert gas. This work has been concerned more with the physical properties of the particles than with the mechanisms of condensation and growth. These mechanisms are main objectives in the work of this laboratory.To obtain the fullest microscopical information about the structure of the particles, careful purification of the supporting gas is necessary and the precipitate must be guarded from the air by a protective coat of gold or gold‐palladium deposited by sputtering under argon or by vacuum evaporation. With the aid of morphological data on a number of volatile metals and thermally stable salts it has been possible to draw some conclusions about the relationship of the particle size and form to the conditions of aerosol generation. Close control of these conditions is especially difficult to achieve with involatile materials, including iron, although it seems likely that the use of lasers could greatly enlarge the scope of these studies in the future.

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