Morphological Transitions during Melting of Small Cylindrical Aggregates

Abstract

Most studies on melting under confinement focus only on the solid and liquid melt phases. Despite of its ubiquity, contributions from the capillary interface (liquid / vapor interface) are often neglected. In this study the melting behavior of small cylindrical aggregates in vapor attached to planar surfaces is analyzed. For the assumed boundary conditions (cylindrical solid with a non wetting top plane and a wettable side wall) solid and the liquid phases can coexist within a certain temperature range. Due to capillary instability, the liquid phase can form either an axisymmetric rouloid morphology or, above a certain threshold liquid volume fraction, a bulge coexisting with a rouloid-like section. The corresponding melting points are different. The analysis explicitly describes the behavior of a real system of small aggregates of long chain alkanes on planar substrates. It also gives qualitative insights into the melting behavior of small aggregates with anisotropic wetting behaviors in general. It reveals in particular how melting points and melting pathways depend on the energetic respectively morphological pathways leading to complete melting.

Hole-initiated melting process of thin films

“…As a result there will be a small temperature range inside which the liquid melt co-exists with the solid. This co-existence can be stable or metastable, and was reported in our previous studies 15,16 .…”

“…In some cases, typically when a large amount of liquid accumulate at a long edge, there are two possible "open" morphologies (Fig. 2), which are (a) uniform channels and (b) bulged morphologies in isobaric (isocurvature) coexistence with channel sections 15,16 . In this work, mostly the bulged morphologies are only possible at such large V l (i.e.…”

“…We have revealed that the emergence of these drops is due to the Plateau-Rayleigh instability of the capillary surface 15 . Later we have analysed the melting behaviour of cylindrical aggregates 16 in gaseous environment based on the same experimental system, and have calculated the deviation of the "de facto" melting point from Gibbs-Thomson equation due to the capillary surface.…”

Alkanes as Intelligent Surface Thermometers: A Facile Approach to Characterize Short‐Lived Temperature Gradients on the Micrometer Scale

“…Additionally, the history of the solidification is preserved in the alkane structure, as they organize to different structures based on the solidification mechanism, which can be optically distinguished (Figure S9, Supporting Information). [ 30,33,34 ] For short‐lived temperature gradients, they follow a logarithmic behavior (Figure 5 and Figures S3 and S6: Supporting Information).…”

“…Their temperature behavior, as well as, their melting and boiling points (here, 37–522 °C) depend on their chain length. [ 30–34 ]…”