Mechanical Robust Nacre-Mimetic Composites with Designable Cryptic Coloration and Electromagnetic Wave-Transparent Performance

Abstract

Ceramic materials are widely used in various protective equipment owing to their excellent mechanical properties and chemical stability, while their applications are limited by monotonous color and poor toughness. Inspired by the colorful and tough natural shells, nacre-mimetic alumina (Al₂O₃)-based (NMA) composites are fabricated by proposing a dual-oxide interface design strategy inspired by the hierarchical structure of natural nacre. The NMA composites achieve color regulation, providing possibilities for their application in camouflage protective armor. The fracture toughness of the optimal NMA composite is more than three times that of commercial Al₂O₃ ceramic. Simultaneously, the NMA composites have obvious advantages in terms of impact resistance compared with Al₂O₃ ceramic and polymer polymethyl methacrylate (PMMA). Additionally, the hierarchical structure of the NMA composites provides favorable structural conditions for transmission of electromagnetic (EM) waves at the frequency band of 18–26.5 GHz. These characteristics make the NMA composites potential protective materials for radar and communication equipment.