THERMOELECTRIC INVESTIGATION OF SOLIDIFICATION OF LEAD .1. PURE LEAD

A technique has been developed to measure very small temperature changes at moving or stationary solid/liquid interfaces in metal wires. The method utilises the temperature-dependent Seebeck potential generated across such interfaces. The present work is novel in that, for the first time, strain effects, which can adversely affect measured results, have been eliminated by the use of unconstrained specimens, and that techniques for producing very fine wire diameter specimens have been developed, greatly extending the velocity range over which kinetic measurements can be made. Undercooling measurements for the planar interface velocity range 0-10000-mu-m/s were thus made, in high purity lead, yielding linear kinetic coefficients for melting (33 +/- 6 cm/s.-degrees-C) and freezing (28 +/- 8 cm/s.-degrees-C) which were not compatible with the classical theory of non-faceted growth, but were in good quantitative agreement with the results of recent molecular dynamics simulations, which indicate that the atomic attachment/detachment process is athermal.