Synergy of CIP@SiO2@C and n-OD@SiO2 microcapsules in achieving dual-functional cement composites for electromagnetic wave absorption and thermal energy storage

This study presents a novel cement-based composite exhibiting dual functionality for both absorbing electromagnetic waves and storing thermal energy. The composite was fabricated by incorporating nano-silica–encapsulated phase change microcapsules (n-OD@SiO 2 , MPCM) and a carbonyl iron powder/amorphous carbon composite absorber (CIP@SiO 2 @C). Its workability, hydration kinetics, electromagnetic properties, thermal behavior, mechanical performance, and internal microstructure were systematically characterized using isothermal calorimetry (TAM), a microwave vector network analyzer (VNA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and three-dimensional X-ray microtomography (Micro-CT). The results show that the combined addition of MPCM and CIP@SiO 2 @C markedly enhances both thermal regulation and electromagnetic wave absorption. The composite containing 20 vol% MPCM and 10 wt% CIP@SiO 2 @C achieved optimal electromagnetic performance, with absorption rates exceeding 80 % across nearly the entire 2–18 GHz and surpassing 85 % within 8–18 GHz. This formulation also demonstrated outstanding thermal regulation, reducing the heating rate by 73 % compared with ordinary cement. Although its mechanical strength was slightly lower than that of plain cement, the optimized composite maintained a 28-day compressive strength of 42.6 MPa, indicating satisfactory structural integrity. The findings underscore the success of the proposed cement-based composite in electromagnetic wave attenuation and thermal management, highlighting its strong potential for applications in electromagnetic pollution mitigation and energy-efficient building materials.