Enhanced microwave absorption properties of core double-shell type Fe@C@BaTiO3 nanocapsules

Microwave absorptions properties of Fe@C@BaTiO3 nanocapsules were investigated in the 1-18 GHz frequency range. High resolution transmission electron microscopy studies reveal that the as-prepared Fe@C@BaTiO3 samples are comprised of the Fe nanoparticles as the core, C and BaTiO3 as middle and outside shells, respectively. Enhanced relative permittivity made the core double-shell Fe@C@BaTiO3 nanocapsules absorbent acquire more efficient complementarities than that of the core single shell Fe@C nanocapsules absorbent between the dielectric loss and magnetic loss. As a result, the microwave absorption properties of Fe@C@BaTiO3-parrafin composites are superior to those of Fe@C-parrafin composites with the improved 1.3-2.0 times of RL values below 20 dB at absorbent thicknesses from 1.35 to 7.00 mm. The optimal reflection loss (RL) of Fe@C@BaTiO3-parrafin composites are 40.2 dB at 8.14 GHz with a thickness of 2.24 mm and the absorption bandwidth of those below 10 dB is 8.4 GHz with only absorbent thicknesses of 1.7-2.0 mm. Moreover, the minimum RL of Fe@C@BaTiO3-parrafin composite shifts to the lower frequency with a thickness range of 1.35-7.00 mm, compared with that of Fe@C-parrafin composite. Furthermore, it is worthy noting that the minimum RL of Fe@C@BaTiO3-parrafin composite is below 20 dB in L-S wave band, which is far superior to that of Fe@C-parrafin composite at the same absorbent layer thicknesses. These results show that the core double-shell type Fe@C@BaTiO3 nanocapsules are great potential microwave absorbents for practical applications. (C) 2015 Elsevier B.V. All rights reserved.