An experimental set-up for the nucleation rate determination in supported undercooled liquid metal droplets

摘要

An experimental laboratory set-up suitable for the processing of undercooled millimetre size liquid droplets supported on inert substrates is described. The apparatus is composed of a high-vacuum chamber and a pyrometric probe with a small area sensitivity. The acquisition-control system, based on a PC with an ADC board, is able to perform repeatedly automatic heating-cooling temperature cycles in which the sample is melted and undercooled. The sample thermal history is acquired during the free radiation cooling phase and the eventual sudden temperature rise associated with crystallization (recalescence) is recorded. A novel approach to determine the nucleation rate of an undercooled liquid from a wide statistical ensemble of recalescence temperatures is proposed. Preliminary results obtained on high purity Ge samples supported on BN substrates are reported. [References: 22]