Structural-Thermal Decoupled Cement-Based Aerogels with Negative Poisson's Ratio for Passive Radiative Cooling

Area of Science:

• Materials Science
• Nanotechnology
• Sustainable Building Technologies

Background:

• Passive radiative cooling (PRC) materials face a trade-off between mechanical fragility and spectral selectivity.
• Robust structural materials often lack the necessary optical properties for efficient cooling.
• Sustainable building thermal management requires advanced materials that are both durable and effective.

Purpose of the Study:

• To develop a mechanically robust and spectrally selective cement-based cooling aerogel (CCA).
• To resolve the conflict between mechanical strength and optical performance in PRC materials.
• To create a bio-inspired material for sustainable building thermal management.

Main Methods:

• Structural-thermal decoupling strategy using synthesized ettringite (AFt) as a mechanical skeleton and infrared emitter.
• Construction of a directionally aligned honeycomb architecture by bridging AFt nanocrystals with poly(vinyl alcohol)/para-aramid nanofibers.
• Characterization of mechanical properties (compressive stress, thermal conductivity, Poisson's ratio) and optical properties (solar reflectance, mid-infrared emissivity).

Main Results:

• The CCA achieved a compressive stress of 43.25 MPa and ultralow thermal conductivity of 0.031 W m-1 K-1.
• Exhibited a strain-dependent negative Poisson's ratio (-0.165), indicating exceptional structural resilience.
• Demonstrated high solar reflectance (0.91) and mid-infrared emissivity (0.96), reducing indoor temperature by 8.5 °C in outdoor tests.

Conclusions:

• The developed CCA offers a paradigm for creating resilient passive radiative cooling materials.
• This bio-inspired, structurally robust aerogel provides a sustainable solution for building thermal management.
• The material's unique hierarchical structure and composition overcome the limitations of traditional cooling materials.