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Surface freezing in n-alkane solutions: the relation to bulk phases.
E Sloutskin1, E B Sirota, H Kraack
1Physics Department, Bar Ilan University, Ramat Gan 52900, Israel.
Summary
Surface freezing in alkane solutions forms a crystalline monolayer with a rotator R(II) structure. This phenomenon
Area of Science:
- Physical Chemistry
- Materials Science
- Surface Science
Background:
- Surface freezing (SF) is a phase transition occurring at the liquid-vapor interface.
- Understanding SF in alkane solutions provides insights into interfacial phenomena and material properties.
Purpose of the Study:
- To investigate surface freezing in tricosane-dodecane alkane solutions.
- To characterize the structure and thermodynamic behavior of the surface frozen layer.
Main Methods:
- Surface tension measurements.
- Synchrotron x-ray surface diffraction.
- Thermodynamic modeling based on ideal solution theory.
Main Results:
- A crystalline surface frozen monolayer with a rotator R(II) structure was identified.
- The monolayer exists within a specific temperature (35-50°C) and concentration (0.3-1.0) range.
- The linear-expansion coefficient of the monolayer was determined as 6.5 x 10⁻⁴ °C⁻¹.
- A thermodynamic model accurately predicted the concentration dependence of the SF temperature.
Conclusions:
- The temperature and concentration ranges of surface freezing are linked to bulk solidification.
- The rotator-liquid dissolution line dictates the observed surface freezing behavior.
- The study provides a comprehensive understanding of surface freezing in alkane mixtures.