Glass waste as a host material for microwave absorption and thermal insulation

This study presents the synthesis, characterization, and performance evaluation of Ni₀.₅Zn₀.₅Fe₂O₄-reinforced foam glass composites as multifunctional materials combining mechanical strength, thermal insulation, and electromagnetic wave (EMW) absorption. Composites with ferrite loadings of 0–60 wt% were fabricated by mixing ferrite powder, foamed glass, and CaCO₃, followed by cold pressing and thermal treatment at 800 °C. The microstructure, porosity, and phase composition were characterized using optical microscopy, EDX, FTIR, and particle size analysis, while mechanical properties were assessed via cold crushing strength and Weibull statistics. The thermal conductivity was measured experimentally and then compared with the values predicted by different theoretical models, and EMW absorption was measured in the S- & C- band for various thicknesses. The results showed a steady increase in compressive strength from 2.59 MPa (0 wt%) to 4.02 MPa (40 wt%), despite high total porosity (up to 71.9%). A thermal insulation value of 0.052 W/m·K was also achieved at 40 wt% ferrite loading. Optimal EMW absorption was achieved at 40 wt% ferrite content. Optimal EMW absorption was achieved at 40 wt% ferrite content, with a minimum reflection loss of −38.5 dB and an effective absorption bandwidth of 5.9 GHz at 5 mm thickness, outperforming non-porous paraffin-based composites. The findings highlight the potential of ferrite-reinforced foam glass as lightweight, mechanically robust, and thermally insulating EMW absorbers for advanced engineering applications.