In this work, NiFe2O4 nanoparticles were successfully supported on cotton-based carbon fibers through a flexible two-step approach consisting of calcination of cotton in a N2 atmosphere and subsequent hydrothermal reaction. The incorporation of the NiFe2O4 nanoparticles into cotton-based carbon fibers resulted in better impedance matching, leading to better microwave absorption performance than cotton-based carbon fibers and NiFe2O4 nanoparticles. For NiFe2O4/carbon fibers, reflection loss (RL) values less than -10 dB were obtained in the frequency range of 11.5-18 GHz with 2.4 mm thickness, which covered the entire Ku-band (from 12 to 18 GHz). Meanwhile, when the matching thickness was 3.2 mm, the RL values less than -10 dB were in the range of 8.0-12.7 GHz, which covered the entire X-band (from 8 to 12 GHz). This excellent and interesting microwave absorption performance can satisfy multiple applications. Owing to the characteristics of a cost-effective synthetic route, low density and excellent microwave absorption, the NiFe2O4/carbon fibers have a promising future in X-band and Ku-band absorption.
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