Enhanced Microwave Absorption of Flake-Oriented Sendust Sheets by Tape Casting

Sendust sheets containing highly in-plane aligned flakes embedded in a nonmagnetic polymer matrix were prepared by tape casting and rolling methods. Experiments indicate that the tape-cast sheets exhibited an improved alignment of flakes along the plane of the sheets, resulting in a pronounced enhancement in complex permeability, compared with those of the rolled sheets. The enhanced permeability was attributed to an induced shape anisotropy field due to the aligned flakes. More interestingly, microwave measurements revealed that a 2 mm-thick tape-cast sheet was measured to have a reflection loss (RL) less than -15 dB. In comparison with that of the rolled sheets, the RL was dramatically reduced by 114%, while the bandwidth less than -10 dB was broadened by 0.7 GHz. These results demonstrate the potential of the tape-cast technique for the production of high-performance microwave absorption sheets.