Melting and solidification of lead nanoparticles embedded in Aluminium-Gallium matrices

Peterlechner M, Moros A, Rösner H, Lazar S, Ericus P, Wilde G

Zusammenfassung

Analyzing the impact of the host matrix on the melting/solidification of embedded Pb nanoparticles,various Ga concentrations (0, 1, 3 and 6 at.%) were added to the Al matrix within the solid solution regimeto modify the mismatch between matrix and nanoparticles by expanding the host lattice. Using transmissionelectron microscopy and differential scanning calorimetry, a strong impact of an atomically flatGa-enriched wetting layer around the Pb nanoparticles on the melting/solidification was observed. The Ga-enrichment was found to be about ~3% above the matrix level, independent of the Ga concentrationin the matrix. It is concluded that upon solidification vacancies arising from the 3.3% volume shrinkage ofliquid Pb are filled by the fast diffusing Ga. The Ga-enriched layer chemically and mechanically decouplesthe matrix from the nanoparticles leading to a more freestanding particle behavior showing strongundercooling upon solidification and reduced or no superheating upon melting.

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