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Published on: May 31, 2022
Beyond Percolation: Graphene-Enabled Network Reinforcement Enhances Thermal Transport in Paraffin Phase-Change
Thomas Hoke1, Jackson Hoke2, Shucheng Guo1
1Department of Electrical and Computer Engineering, University of California, Riverside, California, USA.
Summary
This study introduces hybrid expanded graphite (EG) and graphene nanoplatelet (GNP) fillers for paraffin phase-change materials. These synergistic fillers significantly enhance thermal conductivity at low loadings, enabling efficient thermal management.
Area of Science:
- Materials Science
- Nanotechnology
- Energy Storage
Background:
- Paraffin phase-change materials (PCMs) are crucial for thermal energy storage due to their latent heat properties.
- Low thermal conductivity () in PCMs hinders efficient heat transfer and limits charging-discharging rates.
- Enhancing without compromising energy storage capacity is a key challenge for low-filler-content composites.
Purpose of the Study:
- To investigate the synergistic effects of expanded graphite (EG) worms and graphene nanoplatelets (GNPs) in paraffin composites.
- To achieve significant thermal conductivity enhancement at low filler loadings ().
- To understand the underlying mechanisms responsible for improved thermal transport in hybrid composites.
Main Methods:
- Fabrication of paraffin composites incorporating hybrid EG-GNP fillers at a 1:1 ratio.
- Characterization of thermal conductivity () using standard methods.
- Microscopy (SEM) and micro-computed tomography (microCT) for structural analysis.
- Development of a microCT-informed 3D modeling framework for microstructure-thermal transport correlation.
Main Results:
- At 5 wt% loading, the 1:1 EG-GNP hybrid composite achieved a of 2.7 W/m·K, a significant increase from the base paraffin's 0.25 W/m·K.
- The hybrid fillers outperformed single-filler systems in enhancing thermal conductivity while preserving the melting window and latent heat.
- Microscopy revealed GNPs mitigate EG breakup and reinforce EG structures, while microCT showed a percolating EG backbone.
- A novel graphene-enabled network-reinforcement mechanism was proposed, explaining enhanced intraworm connectivity and heat flux redistribution.
Conclusions:
- Synergistic combination of EG and GNPs offers a highly effective strategy for enhancing the thermal conductivity of paraffin PCMs at low filler concentrations.
- The developed 3D modeling framework provides quantitative insights into structure-property relationships, enabling rational design of advanced thermal management materials.
- This work establishes a quantitative design principle for high-performance hybrid phase-change composites for efficient thermal energy storage.
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