Microwave Absorption Properties of Carbon Black-Carbonyl Iron/Polylactic Acid Composite Filament for Fused Deposition Modeling

A single microwave absorbent and simple coating structure cannot meet the increasing requirements for broadband and strong absorption. Three-dimensional printing is an effective way to prepare multi-component complex structure metamaterial absorbers, and the key is to prepare raw materials with excellent absorption properties, suitable for 3D printing. In this paper, CB-CIP/PLA composite filament was prepared via a high-energy mixer and twin-screw extruder by compounding the dielectric loss material carbon black (CB) and the magnetic loss material carbonyl iron powder (CIP) with polylactic acid (PLA) as the matrix. The coaxial ring test piece was printed by FDM technology, and the microstructure of the composites was observed and analyzed by SEM. Meanwhile, the electromagnetic parameters of the composites were examined by a vector network analyzer, mainly studying the influence of the CB and CIP content and thickness on the microwave absorbing properties of the composite material. The results show that when the CB content is 20% and the CIP content is 30%, the CB-CIP/PLA composite has excellent microwave absorption and broad bandwidth. When the matching thickness is 1.6 mm, the minimum reflection loss (RL) reaches −51.10 dB; when the thickness is 1.7 mm, the effective absorption bandwidth (RL < −10 dB) is 5.04 GHz (12.96−18 GHz), nearly covering the whole Ku band. This work provides an efficient formulation and process to prepare an absorbing composite filament for FDM.