The melting of small particles. II. Bismuth

Abstract

The melting of thin films of bismuth, consisting of individual crystallites, has been investigated in the electron microscope. These films showed an unexpected behaviour in the neighbourhood of the melting point: when an aggregate of particles was held at a constant temperature, the number of particles remaining solid gradually decreased with time, although the actual melting process for each individual particle was extremely fast. This reduction in the number of solid particles with time is approximately exponential. The dependence of the characteristic time for the melting of an aggregate of particles on the temperature and morphology of the particles has been studied in detail. In particular, a platelet form had a sufficiently large time delay, even above the bulk melting point, to allow some of the crystallites to be superheated by up to 7 K.