Melting and supercooling studies in submicron Al particles using valence electron energy-loss spectroscopy in a transmission electron microscope

Abstract

The crystallization behavior of Al and its alloys has been extensively investigated due to the importance of these structural materials. In this study, valence electron energy-loss spectroscopy in a transmission electron microscope was used to study changes that occur in the volume plasmon energy, and hence, the valence electron density, during heating and cooling through the melting temperature in submicron Al particles. The results show that a phonon anharmonicity causes a nonlinear change in the volume plasmon energy that is not present in the liquid phase after melting. The plasmon energy/valence electron density during supercooling is not a direct extrapolation from the liquid state and tends to stabilize, possibly due to local ordering in the liquid. The study also shows that damping of the plasmon excitations in liquid Al is faster compared to solid Al due to electron-phonon interactions and/or Anderson localization of electrons.

Interfacial plasmon at a singular solid-liquid interface in a partially molten aluminum alloy

“…This is consistent with previous studies in liquid Al. 34,35 A unique plasmon feature corresponding to the interface between the crystalline Si and liquid Al is clearly visible in the spectrum image in Fig. 1(b).…”

In-situ extended energy-loss fine structure analysis of the solid and liquid phases in sub-micron Al particles

“…Nearest-neighbor distance change during supercooling of liquid Al Liquid Al can be supercooled 90-100 C below its melting temperature of 660 C prior to its crystallization. 16,18 The nearest-neighbor distance, and for comparison the inverse volume plasmon energy, during heating of solid Al and supercooling of liquid Al from 700 C to 525 C as a function of temperature were plotted in Fig. 4.…”

“…Considerable attention has been given to Al and its alloys as they are important light-weight structural materials. 15 Their melting and crystallization behavior has been studied by various techniques such as droplet, 16 emulsion and calorimetry, 17 and electron energy-loss spectroscopy (EELS), 18 etc. The present EXELFS study was undertaken to follow and understand the behavior of the first nearest-neighbor atom distances during heating and cooling of solid and liquid Al in situ in a TEM.…”

Developments on Thermometric Techniques in Probing Micro- and Nano-heat

“…When an electron beam created by STEM penetrates a sample, a bulk plasmon with energy E will be excited. According to the free-electron model, this energy is proportional to the square root of the valence electron density (n) of sample and can be [54][55][56][57] correspondingly detected by EELS. As thermal expansion changes this electron density and thereby changes the plasmon energy, the temperature can be deduced from the plasmon energy shift measured by EELS and vice versa.…”