High Microwave Absorption of Multi-Walled Carbon Nanotubes (Outer Diameter 10 – 20 nm)-Epoxy Composites in R–Band
John I. Ejembi
Department of Physics, Southern University and A&M College, Baton Rouge, LA 70813, USA and Department of Geology, Southern Illinois University Carbondale, IL 62901, USA
Ifeanyi H. Nwigboji
Department of Physics, Southern University and A&M College, Baton Rouge, LA 70813, USA
Zhou Wang
Department of Physics, Southern University and A&M College, Baton Rouge, LA 70813, USA
Diola Bagayoko
Department of Physics, Southern University and A&M College, Baton Rouge, LA 70813, USA
Guang- Lin Zhao *
Department of Physics, Southern University and A&M College, Baton Rouge, LA 70813, USA
*Author to whom correspondence should be addressed.
Abstract
We studied the microwave absorption of multi-walled carbon nanotubes (MWCNTs)-epoxy composites over a continuous frequency range in R-band (26.5 – 40 GHz). The outer diameters (OD) of the MWCNTs were in the 10 – 20 nm range. We measured and analyzed the microstructures, dielectric and the microwave absorption properties of the composite samples. High attenuation factor which correlates significant absorption of microwave was observed in the 32 – 40 GHz frequency band. Microwave absorption was due to high dielectric losses, interfacial charge polarization, and the free electron mobility in the composite material. Our results also show the dependence of microwave absorption on the loading fractions of MWCNTs and on the thickness of the absorbing material. Significant microwave absorption capabilities of the composite samples were achieved at 7 to 10 wt.% of MWCNT loadings for frequencies above 32 GHz.
Keywords: Composites, nanotubes, dielectric properties, conducting polymers, microwave absorption