Simultaneous Improvement of Bendability and Passive Daytime Radiative Cooling Performance in Multilayer Alumina Fiber...

Area of Science:

• Materials Science
• Nanotechnology
• Thermal Engineering

Background:

• Passive daytime radiative cooling (PDRC) materials need high solar reflectance and atmospheric window emissivity.
• Porous structures used for high solar reflectance can compromise mechanical reliability.
• A trade-off exists between optical properties and mechanical stability in PDRC materials.

Purpose of the Study:

• To develop a PDRC material that overcomes the trade-off between optical performance and mechanical reliability.
• To engineer a layered alumina nanofiber membrane (LANM) with enhanced cooling and mechanical properties.
• To investigate the structure-property relationships in the designed LANM.

Main Methods:

• Dual-nozzle electrospinning to create alternating layers of alumina and sacrificial polyvinyl alcohol (PVA).
• Programmed deposition and removal of interlayers to form a layered architecture with air gaps.
• Characterization of optical properties (solar reflectance, emissivity) and mechanical properties (bending deformability, stress transfer).

Main Results:

• The LANM demonstrated simultaneous regulation of solar-band scattering and bending load transfer.
• Achieved a maximum sub-ambient temperature reduction of ~5.8 °C in outdoor tests, outperforming monolithic alumina nanofiber (ANM) by ~2.4 °C.
• The layered structure improved bending deformability through a multiple-neutral-axis mechanism and segmented stress transfer.

Conclusions:

• The developed LANM effectively addresses the mechanical limitations of traditional PDRC materials.
• The micro-layered architecture is crucial for enhancing scattering while maintaining high emissivity.
• This approach offers a promising pathway for robust and efficient passive radiative cooling applications.