Highly Thermo-Conductive Three-Dimensional Graphene Aqueous Medium
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-07-01 |
| Journal | Nano-Micro Letters |
| Authors | Zheng Bo, Chongyan Ying, Huachao Yang, Shenghao Wu, Jinyuan Yang |
| Institutions | Zhejiang University, University of Hong Kong |
| Citations | 14 |
| Analysis | Full AI Review Included |
Highly Thermo-Conductive Three-Dimensional Graphene Aqueous Medium
Section titled âHighly Thermo-Conductive Three-Dimensional Graphene Aqueous MediumâExecutive Summary
Section titled âExecutive Summaryâ- Core Innovation: The development of a novel 3D Graphene Structure with Covalent-Bonding Nanofins (3D-GS-CBF) used as an ultralow-loading filler for highly thermo-conductive aqueous mediums.
- Record Thermal Performance: Achieved a thermal conductivity (k) of 2.61 W m-1 K-1 at a minimal filler loading of only 0.26 vol%.
- Efficiency Benchmark: The Thermal Conductivity Enhancement Efficiency (TCEE) reached a record high of 1300%, which is approximately six times greater than the highest previously reported aqueous mediums.
- Mechanism Validation: Multiscale modeling (NEMD and FEM) confirmed that the covalent-bonding nanofins significantly increase the surface area and enhance heat exchange at the graphene-water interface, resulting in a very low interfacial thermal resistance (Ri = 6.7 x 10-9 K m2 W-1).
- Long-Term Stability: The robust 3D covalent architecture provides excellent stability, maintaining structure in solution for greater than 6 months, addressing a major drawback of conventional non-covalent graphene networks.
- Practical Impact (Solar): The medium enhanced solar vapor evaporation efficiency to 70.8%, improving the evaporation rate by 1.5 times compared to conventional counterparts.
- Practical Impact (Cooling): Demonstrated superior thermal management for high-power LEDs, achieving a lower working temperature (45.2 °C) than commercial coolants.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Thermal Conductivity (k) | 2.61 | W m-1 K-1 | 3D-GS-CBF aqueous medium (0.26 vol%) |
| Thermal Conductivity Enhancement Efficiency (TCEE) | 1300 | % | Enhancement per 1% filler loading |
| Filler Volume Fraction | 0.26 | vol% | Required loading for peak k |
| Interfacial Thermal Resistance (Ri) | 6.7 x 10-9 | K m2 W-1 | Graphene-water interface (NEMD result) |
| Solar Vapor Generation Efficiency | 70.8 | % | 3D-GS-CBF aqueous medium (1 sun) |
| Solar Evaporation Rate | 1.13 | kg m-2 h-1 | 3D-GS-CBF aqueous medium |
| LED Working Temperature (3D-GS-CBF) | 45.2 | °C | Thermal management application |
| LED Working Temperature (Commercial Coolant) | 49.0 | °C | Water/ethylene glycol baseline |
| Operation Current Reduction (LED Cooling) | 18.3 | % | Reduction achieved using 3D-GS-CBF |
| Nanofin Height | ~400 | nm | Typical height of graphene nanofins on skeleton |
| Equilibrium Contact Angle | ~5.17 | ° | Super-hydrophilic nature of 3D-GS-CBF surface |
| Long-Term Stability | >6 | months | Stability in aqueous solution |
Key Methodologies
Section titled âKey Methodologiesâ- Template Preparation: Commercial Ni foam (1.6 mm thick) was used as the sacrificial template and placed in a cylindrical quartz tube (43 mm internal diameter).
- 3D Graphene Skeleton Synthesis (PECVD): The tube was evacuated (3 Pa) and heated to 700 °C. An inductively coupled plasma (ICP) source (250 W RF power) was used. CH4 (5 mL min-1) and H2 (5 mL min-1) were introduced, maintaining chamber pressure at 30 Pa for 1 hour.
- Covalent-Bonding Nanofin Growth: The dried 3D-GS sample was functionalized using 500 ppm moist ozone flow (1 L min-1) for 5 minutes to promote the growth of covalent-bonding nanofins (3D-GS-CBF).
- Template Removal: The graphene-Ni foam was coated with polymethyl methacrylate (PMMA) solution (4 wt% in ethyl lactate), dried at 80 °C, and then immersed in 3 M HCl solution at 80 °C overnight to dissolve the Ni template. PMMA was subsequently removed with hot acetone (50 °C).
- Thermal Characterization: Thermal diffusivity (a) of the aqueous medium was measured using a laser flash analysis apparatus (NETZSCH LFA467 Nanoflash). Thermal conductivity (k) was calculated using the relationship k = Ďac.
- Structural Analysis: Morphology and structure were characterized using Scanning Electron Microscopy (SEM, Hitachi SU-70), Transmission Electron Microscopy (TEM, Tecnai G2 F20S-TWIN), and High-Resolution TEM (HRTEM) to confirm covalent bonding.
- Multiscale Modeling: Non-equilibrium Molecular Dynamics (NEMD) simulations, utilizing the AIREBO potential, were performed to calculate the interfacial thermal resistance (Ri). These results were integrated into Finite Element Models (FEM) using COMSOL Multiphysics 5.3a to simulate macro-scale heat transport and temperature evolution.
Commercial Applications
Section titled âCommercial Applicationsâ- High-Performance Nanofluids: Creation of stable, highly efficient heat transfer fluids for industrial cooling loops, leveraging the 1300% TCEE at extremely low filler concentrations.
- Thermal Management of Electronics: Superior coolants for high-power density devices, including LEDs, CPUs, and data center components, offering lower operating temperatures and reduced energy consumption compared to commercial coolants.
- Solar Energy Systems: Enhancing the efficiency of volumetric solar thermal conversion systems for direct vapor generation, providing a pathway for high-performance solar energy harvesting without complex interfacial heating setups.
- Advanced Heat Exchangers: Integration into microchannel and compact heat exchanger designs where the high thermal conductivity of the aqueous medium can maximize heat flux density.
- Chemical and Photothermal Catalysis: Potential use in boosting reaction kinetics by rapidly and uniformly increasing the temperature of the aqueous medium, particularly for processes requiring precise thermal control.