Carbon nanotube-CdS core-shell nanowires with tunable and high-efficiency microwave absorption at elevated temperature

Tuning microwave absorption to meet the harsh requirement of thermal environments is a great challenge. Three kinds of nanowires, including multi-walled carbon nanotubes (MWCNTs) coated with CdS nanocrystals (CdS-MWCNTs), and MWCNTs coated with different-thickness CdS sheaths, have been synthesized through mild solution-process synthesis. The influence of CdS amount, external temperature, loading concentration and sample thickness on the absorption performance were studied. The composite loading with 6 vol.% CdS-MWCNTs shows the best absorption of -47 dB at 473 K with a thickness of 2.6 mm in the temperature range of 323-573 K and X band. The effective bandwidth covers the full X band in 323-473 K for RL <= -20 dB and reaches 2.0 GHz at 473 K for RL <= -20 dB. The enhanced absorption ability of CdS-MWCNTs arises from the effective impedance matching, benefiting from abundant interfacial polarization from the added CdS nanocrystals and the changeable dielectric property at elevated temperature. The results indicate that the CdS-MWCNT is a promising functional material for high temperature microwave absorption.