An atomically smooth container: Can the native oxide promote supercooling of liquid gallium?
Ishan D. Joshipura,
Chung Kim Nguyen,
Colette Quinn,
Jiayi Yang,
Daniel H. Morales,
Erik Santiso,
Torben Daeneke,
Vi Khanh Truong,
Michael D. Dickey
Affiliations
Ishan D. Joshipura
Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
Chung Kim Nguyen
School of Engineering, STEM College, RMIT University, Melbourne, VIC 3000, Australia
Colette Quinn
TA Instruments, Salt Lake City, UT, USA
Jiayi Yang
Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
Daniel H. Morales
Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
Erik Santiso
Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
Torben Daeneke
School of Engineering, STEM College, RMIT University, Melbourne, VIC 3000, Australia
Vi Khanh Truong
Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA; College of Medicine and Public Health, Flinders University, Adelaide, SA 5042, Australia; Corresponding author
Michael D. Dickey
Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA; Corresponding author
Summary: Metals tend to supercool—that is, they freeze at temperatures below their melting points. In general, supercooling is less favorable when liquids are in contact with nucleation sites such as rough surfaces. Interestingly, bulk gallium (Ga) can significantly supercool, even when it is in contact with heterogeneous surfaces that could provide nucleation sites. We hypothesized that the native oxide on Ga provides an atomically smooth interface that prevents Ga from directly contacting surfaces, and thereby promotes supercooling. Although many metals form surface oxides, Ga is a convenient metal for studying supercooling because its melting point of 29.8°C is near room temperature. Using differential scanning calorimetry (DSC), we show that freezing of Ga with the oxide occurs at a lower temperature (−15.6 ± 3.5°C) than without the oxide (6.9 ± 2.0°C when the oxide is removed by HCl). We also demonstrate that the oxide enhances supercooling via macroscopic observations of freezing. These findings explain why Ga supercools and have implications for emerging applications of Ga that rely on it staying in the liquid state.
