A nacre-inspired structural material with thermochromic properties and mechanical robustness by atomic-level design

Area of Science:

• Materials Science
• Biomimetics
• Nanotechnology

Background:

• Advanced structural materials require a balance of lightweight, high strength, and toughness.
• Biomimetic approaches offer potential for achieving these properties.
• Existing biomimetic materials lack integrated fire-warning and flame-retardant functionalities.

Purpose of the Study:

• To develop a nacre-mimetic composite with mechanical robustness, thermochromic fire warning, and flame-retardant properties.
• To integrate active fire detection and passive flame retardancy into structural materials.
• To enhance safety for applications in fire-prone environments.

Main Methods:

• Fabrication of a nacre-mimetic alumina-cyanate resin composite (NAC).
• Incorporation of chromium atoms into alumina microplatelets via atomic doping for thermochromism and strengthening.
• Utilizing a bioinspired 'brick-and-mortar' architecture.
• Employing a machine-learning-based image-recognition system for fire detection.

Main Results:

• The NAC composite achieved high strength (∼290.1 MPa) and fracture toughness (∼11.1 MPa m^1/2).
• Thermochromic properties enabled rapid fire warning (within 9 s at 250°C).
• Layered structure provided excellent flame retardancy with an oxygen-limiting index of 50%, reducing heat release.

Conclusions:

• The developed nacre-mimetic composite successfully integrates structural integrity with active fire warning and passive flame retardancy.
• This material design offers a promising pathway for advanced fire-warning systems in challenging environments.
• The combination of biomimicry, thermochromism, and flame retardancy enhances material safety and functionality.