Magnetic aligned Fe3O4-reduced graphene oxide/waterborne polyurethane composites with controllable structure for high microwave absorption capacity

Fe3O4-reduced graphene oxide (FRGO)/waterborne polyurethane (WPU) composites with controllable structure and high microwave absorption capacity were developed. The aligned structure of FRGO in the FRGO/WPU composites was realized by a magnetic-field-induced method. WPU dispersion with nano-scaled particles could suppress the aggregation of FRGO during the drying process. The FRGO/WPU composites have much high complex permittivity, dielectric loss tangent, and microwave absorption capacity owing to the magnetic alignment. WPU with 2% FRGO achieved the minimum reflection loss value of -67.8 dB, which can be attributed to the orientation and three-dimensional structure of FRGO. The effective bandwidth wider than 14 GHz can be reached by a combination of two layers of composites with different permittivity through theoretical calculation. The aligned FRGO/WPU composites have a great future in the application of microwave absorption materials. (C) 2019 Elsevier Ltd. All rights reserved.