Molten-salt-assisted combustion synthesis of B4C powders with high specific area and their electromagnetic wave absorbing performance

Abstract

Novel dielectric boron carbide (B4C) microwave absorbers have attracted extensive research interest. In this study, B2O3, polyvinyl chloride (PVC), Mg, and NaCl powders were used to prepare submicron-sized B4C powders with high specific surface areas via molten-salt-assisted combustion synthesis. The XRD, Raman, SEM-EDS, and BET were performed to characterize the effects of the NaCl content on the phase compositions and microstructures of the different samples. The results indicated that the grain size of the B4C powders initially decreased and then increased with increasing NaCl content. Particularly, the P-6 sample (6 wt% NaCl) exhibited the smallest B4C grains (0.1 μm) and highest specific surface area (9.06 g/cm2) among these samples. Finally, the electrical conductivities, dielectric performances, and electromagnetic wave (EMW)-absorbing performances of the samples were studied, and the dominant absorber loss mechanism was elucidated. With an optimal material thickness, the P-6 sample exhibited the minimum reflection loss (−42.42 dB) and the widest effective absorption bandwidth (3.4 GHz). Overall, these results verify that B4C powders with high specific surface areas and excellent EMW-absorbing properties can be easily synthesized.