Effect of heat treatment on ZrO2-embedded electrospun carbon fibers used for efficient electromagnetic interference shielding

ZrO2-embedded carbon fibers were prepared for use as an electromagnetic interference (EMI) shielding material by electrospinning and heat treatment methods. Structural changes were observed in the ZrO2 and in the carbon structures by XRD and Raman spectroscopy, respectively. During heat treatment, XRD analysis results revealed a transition from a monoclinic structure to a tetragonal structure in ZrO2 and a graphitization in the structural formation of carbon fibers was observed by Raman spectroscopy. It was observed that these structural changes in the ZrO2 and the carbon fibers improved the real and imaginary permittivities by a factor of more than 3.5. The EMI shielding efficiency (SE) improved along with the permittivity with higher treatment temperatures and greater amounts of embedded ZrO2; the highest average EMI SE achieved was 31.79 dB in 800–8500 MHz. The heat treatment played an important role in the improvements in the permittivity and in the EMI SE because of the heat-induced structural changes of the ZrO2-embedded electrospun carbon fibers. We suggest that the EMI shielding of the fibers is primarily due to the absorption of electromagnetic waves, which prevents secondary EMI by reflection of electromagnetic waves.

For all of the samples, over 88% of the EMI SE was due to absorption. This highly efficient absorption of electromagnetic waves is attributed to the high permittivity of graphite-structured carbon and tetragonal-structured ZrO2, which resulted from the heat treatment.Figure optionsDownload as PowerPoint slideHighlights
► High permittivity by structure transition of ZrO2 from monoclinic to tetragonal.
► Improved permittivity by graphitization of carbon fibers using thermal treatment.
► Suggested mechanism for shielding electromagnetic waves by adsorption.