A DIRECT OBSERVATION OF LOW-DIMENSIONAL EFFECTS ON MELTING OF SMALL LEAD PARTICLES

The melting of small lead particles embedded in a silicon monoxide matrix has been studied by dark-field electron microscopy. Thomson’s idea from 1888, that the melting temperature depends on the size of the particles and Faraday’s idea from 1860, that melting of the surface occurs below the bulk melting temperature, are demonstrated here straightforwardly. The electron microscope pictures give the most direct observation on the existence of a molten surface layer in equilibrium with a solid core at temperatures below the melting point. The width of the molten layer is demonstrated to depend on the particle curvature as well as on temperature indicating a continuous transition. Quantitatively, it was found that for the small lead particles, the width of the molten layer is wider than the reported one for bulk lead. © 1990 IOP Publishing Ltd.