Multifunctional Hierarchical Metamaterial for Thermal Insulation and Electromagnetic Interference Shielding at...

Lightweight cellular materials are of growing interest due to their potential for enhanced mechanical and functional performance. Prior research has shown that such materials can offer benefits in structural applications, but their use in ceramics is limited by brittleness and strength loss at high temperatures. This gap motivated the development of new composite structures that maintain mechanical integrity while enabling multifunctional properties. Existing solutions have not fully addressed the challenge of combining high strength with thermal and electromagnetic performance. The need for materials that perform well under extreme conditions remains unmet. Current methods struggle to balance structural stability with functional versatility. This study aims to address these limitations by introducing a novel composite design. The focus is on achieving both mechanical resilience and multifunctionality in a single material system. The novelty lies in integrating hierarchical structures with metamaterial properties to overcome prior constraints.

The goal of this research is to develop a ceramic matrix composite metamaterial (CCM) that combines mechanical strength with thermal and electromagnetic interference shielding capabilities. The specific problem involves creating a material that retains its properties at elevated temperatures while maintaining structural stability. The motivation stems from the limitations of traditional ceramic composites, which often fail under high-stress or high-temperature conditions. The researchers propose a solution using hierarchical structures and a negative Poisson's ratio design. This approach allows the material to exhibit superelasticity and high compressive strength. The study also aims to evaluate the material's performance in thermal insulation and EMI shielding. The researchers are testing whether the hierarchical structure can enable multifunctional behavior without compromising mechanical integrity. The ultimate aim is to provide a scalable and practical material for advanced engineering applications.

The researchers employed centripetal freeze-casting to fabricate the ceramic matrix composite metamaterial (CCM). This technique allows for the creation of hierarchical structures with controlled porosity and alignment. The CCM was designed to exhibit a negative Poisson's ratio, which contributes to its superelastic behavior. Mechanical testing was conducted to assess compressive strength and specific modulus. The relationship between density and modulus was analyzed to confirm the material's metamaterial characteristics. Thermal conductivity measurements were performed to evaluate insulation performance. Electromagnetic interference shielding efficiency was tested at room temperature and at 700 °C to assess high-temperature stability. The hierarchical structure was optimized to enhance both mechanical and functional properties. The study combined experimental fabrication with performance evaluation to validate the material's multifunctional capabilities.

The CCM exhibited a negative Poisson's ratio with a value as low as -0.16 under compression. The specific modulus of the material followed the relationship E ∼ ρ^1.3, indicating high specific strength. The material maintained its mechanical properties even under high compressive loads. Thermal conductivity was measured at 30.62 mW·m⁻¹·K⁻¹, suggesting good thermal insulation. At room temperature, the EMI shielding efficiency reached 40 dB. The specific EMI shielding efficiency per unit thickness (SSE/t) was 9416 dB·cm²·g⁻¹ at 700 °C. This value is 100 times higher than that of traditional ceramic matrix composites. The hierarchical structure and metamaterial design contributed to the material's multifunctional performance.

The study demonstrates that the CCM can maintain a negative Poisson's ratio and high specific strength at elevated temperatures. The hierarchical structure and metamaterial design enable the material to exhibit superelasticity and stability. The CCM also provides excellent thermal insulation and EMI shielding properties. The researchers propose that the material's performance is due to its unique structural design. The specific EMI shielding efficiency at 700 °C is significantly higher than that of conventional composites. The material's multifunctional behavior supports its potential for advanced engineering applications. The study suggests that hierarchical structures can be used to optimize both structural and functional performance. The findings may guide future developments in lightweight, multifunctional materials.