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Synergistic Dual-Mode Cooling Enabled by h-BN/Al2O3 Hybrid Composites for Efficient Thermal Management
Yubeen Oh1, Jeehoon Yu1, Hyungu Im2
1Department of Advanced Materials Engineering, Chung-Ang University, Anseong 17546, Republic of Korea.
ACS Applied Materials & Interfaces
|October 1, 2025
Summary
This study introduces a novel hybrid composite sheet for passive radiative cooling. The material achieves significant subambient temperatures, offering a breakthrough in thermal management for various applications.
Area of Science:
- Materials Science
- Nanotechnology
- Thermal Engineering
Background:
- Effective thermal management is crucial for energy efficiency and device longevity.
- Passive radiative cooling materials offer a sustainable solution to reduce energy consumption for cooling.
- Existing materials often face limitations in broadband solar reflectance and thermal conductivity.
Purpose of the Study:
- To develop a high-performance, millimeter-thick, free-standing hybrid composite sheet for enhanced thermal management and energy efficiency.
- To integrate microscale hexagonal boron nitride (h-BN) platelets and nanoscale alumina (Al2O3) nanoparticles within an epoxy matrix.
- To achieve broadband solar reflectance and high mid-infrared emittance for effective passive cooling.
Main Methods:
- Fabrication of a hybrid composite sheet using h-BN platelets and Al2O3 nanoparticles in an epoxy matrix.
- Characterization of optical properties, including solar reflectance (UV-vis, NIR) and mid-infrared emittance.
- Measurement of out-of-plane thermal conductivity.
- Theoretical simulations for net cooling power.
- Field testing of the composite sheet for subambient temperature drop and daily cooling performance.
Main Results:
- The composite sheet exhibits 80% average reflectance in UV-vis and 92% in NIR.
- Achieved a mid-infrared emittance of 85%.
- Demonstrated excellent out-of-plane thermal conductivity of 6.72 W m-1 K-1.
- Theoretical simulations predicted a net cooling power of up to 141 W m-2.
- Field tests showed a peak subambient temperature drop of -12.4 °C and an average of -10.2 °C.
Conclusions:
- The developed hybrid composite sheet offers significant advancements in passive radiative cooling.
- The material demonstrates superior thermal management capabilities, enabling bulk cooling beyond surface effects.
- Potential applications include buildings, stationary electronics, and mobile platforms like UAVs.
- The electrically insulating, corrosion-resistant nature further enhances its suitability for diverse applications.
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