Preparation and characterizations of Fe3O4/n-OD@SiO2@C composite microcapsule for electromagnetic wave absorption and heat storage dual-functional cement-based composite material

This study develops innovative cement-based composites with integrated electromagnetic wave absorption and thermal energy storage capabilities by incorporating Fe₃O₄/n-OD@SiO₂@C core-shell microcapsules. These microcapsules feature a hierarchical structure consisting of a Fe₃O₄/n-octadecane (n-OD) composite core, an intermediate amorphous SiO₂ layer, and an outer carbon coating. Structural and functional characterization using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and vector network analysis (VNA) confirmed the structural integrity and multifunctionality of Fe₃O₄/n-OD@SiO₂@C. The results demonstrate that the incorporation of Fe₃O₄/n-OD@SiO₂@C significantly enhances both electromagnetic wave absorption and thermal energy storage in cement-based materials. The composite containing 50 vol% expanded polystyrene (EPS), 10 wt% Fe₃O₄/n-OD@SiO₂@C, and 5 wt% adhesive exhibits optimal electromagnetic wave absorption performance, dissipating 80 % of electromagnetic wave absorption rate across the 8.5–18 GHz frequency spectrum. Simultaneously, this formulation demonstrates exceptional thermal regulation capabilities, decreasing the heating rate by 90.6 % compared to conventional Portland cement. While the addition of EPS and microcapsules leads to a reduction in compressive strength, the composite still meets non-load-bearing structural requirements while enabling simultaneous electromagnetic wave absorption and thermal energy regulation. These findings highlight the potential of this material for advanced building envelopes in energy-efficient infrastructure, offering dual electromagnetic and thermal management capabilities. • Fe 3 O 4 @SiO 2 @C composite microcapsules are consisted of a dual-phase core encapsulated by a dual-layer protective shell. • The incorporation of Fe 3 O 4 @SiO 2 @C enhances both wave absorption and heat storage capacity in cementitious matrices. • The cement-based material with 50 vol% EPS, 10 wt% Fe 3 O 4 @SiO 2 @C and 5 wt% adhesive achieves multifunctional performance. • The developed cement-based composites are suitable for non-load-bearing building structures.