Electromagnetic and microwave absorbing properties of multi-walled carbon nanotubes/polymer composites

The preparation and characterization of CNTs/polymer (PET, PP, PE and varnish) composites were studied for microwave absorption applications in the range of 2–18 GHz. The results indicated the position of reflectivity peak moves to a lower frequency and the loss factors of composites increase with increasing CNTs concentrations. When CNTs concentration was above 4 wt%, there was a sharp increase of loss tangent. 4 wt% CNTs/PET and 8 wt% CNTs/varnish composites had considerable absorbing peak at 7.6 GHz, 15.3 GHz and achieved maximum absorbing value of 17.61 dB, 24.27 dB, respectively. In addition, the frequencies range for absorbing values exceeding 5 dB of CNTs/(PET, PP, varnish) composites are 13 GHz, 10 GHz and 6 GHz, respectively. The microwave absorption of CNTs composites can be mainly attributed to the dielectric loss rather than magnetic loss.