ISSN:
1573-4803
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Maschinenbau
Notizen:
Abstract Condensation aerosols of bismuth were prepared in the heat-pulse cloud chamber at various wall temperatures by flash evaporation of metal into argon at atmospheric pressure. The particles nucleate from the vapour in the liquid state only. When prepared at low wall temperatures the droplets solidify to tapered twins with an asymmetrically sited protuberance. At wall temperatures approaching the melting point of the metal the morphology of the smaller particles is affected by thermal ageing. Complex multiple twins occur, as well as twins of simpler, rhombohedral shape. A solidification mechanism is proposed for the tapered particles, by which the freshly nucleated crystal, growing at the surface of the droplet with an emergent corner, experiences a twinning shear under the influence of fluctuating stresses imposed by the particle motion. The crystal growth rate is thereby enhanced unidirectionally, and the particle becomes elongated as a result of the volumetric expansion.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF01113777
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