Thermal analysis of Al droplet crystallization and modeling of the nucleation process: how to interpret experimental data?

0545284 - FZÚ 2022 RIV US eng A - Abstract
Kožíšek, Zdeněk - Král, Robert - Zemenová, Petra
Thermal analysis of Al droplet crystallization and modeling of the nucleation process: how to interpret experimental data?
American Conference on Crystal Growth and Epitaxy (ACCGE-22). Virtual: ACCGE, 2021. s. 295-295.
[American Conference on Crystal Growth and Epitaxy (ACCGE-22) / 20th US Workshop on Organometallic Vapor Phase Epitaxy OMVPE /20./. 02.08.2021-04.08.2021, Virtual Conference]
R&D Projects: GA MŠMT(CZ) EF16_019/0000760
Grant - others:OP VVV - SOLID21(XE) CZ.02.1.01/0.0/0.0/16_019/0000760
Institutional support: RVO:68378271
Keywords : DSC * crystallization * nucleation * aluminum
OECD category: Condensed matter physics (including formerly solid state physics, supercond.)

The crystallization of Aluminum (Al) droplet was detected by the Differential Scanning Calorimetry (DSC) at the temperature Tc = 642 C (undercooling 18 K) using broad range of cooling rates 2-20 K/min. In the next step, the repeated DSC measurements at the isothermal conditions with undercooling of ca. 6 K discovered that the crystallization event occured after relatively long time delay 10-50 min. Experimental data confirmed the stochastic nature of crystal nucleation similarly to other systems. We analyzed the DSC data using the Johnson-Mehl-Avrami (JMA) model and also via numerical solution of the standard kinetic model of nucleation. In this case, the JMA model fails as the dimensionality of the growth is unrealistic. The crystallization probably occurs by a two-step mechanism, i.e. when the structure of small sub-critical clusters differs from the larger ones and thus the nucleation kinetics is slow.

Permanent Link: http://hdl.handle.net/11104/0322016