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Superheating of grain boundaries within bulk colloidal crystals
Xiuming Xiao1, Lilin Wang2, Zhijun Wang2
1Key Laboratory of Soft Condensed Matter Physics and Smart Materials, College of Physics, Chongqing University, Chongqing, 401331, China.
Nature Communications
|March 25, 2022
Summary
Grain boundaries (GBs) in colloidal crystals can be superheated, melting via heterogeneous nucleation. This study experimentally confirms superheating of GBs, challenging previous assumptions about premelting.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Physical Chemistry
Background:
- The phenomenon of premelting at grain boundaries (GBs) in crystalline solids is a long-standing question due to experimental challenges.
- Direct observation of melting dynamics at GBs requires high-resolution techniques.
Purpose of the Study:
- To experimentally investigate the premelting behavior of grain boundaries (GBs) in bulk colloidal crystals.
- To determine if GBs can be superheated and to elucidate the nucleation mechanism of melting.
Main Methods:
- Utilized focused optical beam to locally heat single GBs in hard-sphere colloidal crystals.
- Observed melting dynamics at single-particle resolution using video microscopy.
- Analyzed Lindemann parameter and critical nucleus size for melting point determination.
Main Results:
- All GBs, including high-energy ones, were observed to superheat and melt via heterogeneous nucleation.
- Measured incubation time and contact angle to compute kinetic factors, energy barriers, and nucleation rates.
- Determined superheat limits for GBs with various misorientations, revealing instability mechanisms.
Conclusions:
- Experimental evidence confirms the superheating of GBs in colloidal crystals.
- Under local heating, GBs exhibit superheating and heterogeneous nucleation, contrasting with uniform heating where premelting is limited to triple junctions.
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