Microwave-pyrolyzed recovered carbon fibers for electromagnetic wave absorption

The recycling and utilization of carbon fibers have garnered significant research interest in recent years. Nevertheless, current recycling pathways for reclaimed carbon fibers remain constrained, with reprocessed products exhibiting limited economic value. This study investigates a two-step microwave pyrolysis recycling methodology, investigating the performance of microwave-pyrolyzed recycled CF (mCF) and systematically studying the effect of oxidation time on the properties of the recycled fibers. The prolonged oxidation time leads to a progressive reduction of carbonaceous residues on the fiber surfaces. At an oxidation duration of 25 min, mCF achieves an optimal tensile strength retention rate of 86.2 %. Notably, the presence of polar functional groups and surface defects on mCF enhances dipole polarization while elongating the propagation path of electromagnetic waves, thereby endowing mCF with superior microwave absorption characteristics. Under conditions of low filler loading (20 wt%) and minimal thickness (4.5 mm), mCF exhibits exceptional electromagnetic wave attenuation performance, achieving a minimum reflection loss (RL) of −15.17 dB and an effective absorption bandwidth (RL ≤ −10 dB) of 1.72 GHz. These findings establish mCF as a promising multifunctional filler that synergistically combines mechanical robustness with outstanding microwave absorption properties, proposing an innovative paradigm for the high-value resource utilization of recycled carbon fibers.