Abstract
BackgroundCarbon nanotube (CNT) characteristics, besides the processing conditions, can change significantly the microwave absorption behavior of CNT/polymer composites. In this study, we investigated the influence of three commercial multi-walled CNT materials with various diameters and length-to-diameter aspect ratios on the X-band microwave absorption of epoxy nanocomposites with CNT contents from 0.125 to 2 wt%, prepared by two dispersion methods, i.e. in solution with surfactant-aiding and via ball-milling.ResultsThe laser diffraction particle size and TEM analysis showed that both methods produced good dispersions at the microscopic level of CNTs. Both a high aspect ratio resulting in nanotube alignment trend and good infiltration of the matrix in the individual nanotubes, which was indicated by high Brookfield viscosities at low CNT contents of CNT/epoxy dispersions, are important factors to achieve composites with high microwave absorption characteristics. The multi-walled carbon nanotube (MWCNT) with the largest aspect ratio resulted in composites with the best X-band microwave absorption performance, which is considerably better than that of reported pristine CNT/polymer composites with similar or lower thicknesses and CNT loadings below 4 wt%.ConclusionsA high aspect ratio of CNTs resulting in microscopic alignment trend of nanotubes as well as a good level of micro-scale CNT dispersion resulting from good CNT-matrix interactions are crucial to obtain effective microwave absorption performance. This study demonstrated that effective radar absorbing MWCNT/epoxy nanocomposites having small matching thicknesses of 2–3 mm and very low filler contents of 0.25-0.5 wt%, with microwave energy absorption in the X-band region above 90% and maximum absorption peak values above 97%, could be obtained via simple processing methods, which is promising for mass production in industrial applications.Graphical Comparison of the X-band microwave reflection loss of epoxy composites of various commercial multi-walled carbon nanotube materials.
Highlights
Carbon nanotube (CNT) characteristics, besides the processing conditions, can change significantly the microwave absorption behavior of Carbon nanotubes (CNTs)/polymer composites
Ball-milling treatment of the as-synthesized Nanocyl NC700 multi-walled carbon nanotube (MWCNT) to alter the CNT length and bulk density resulting in a change in the electrical conductivity of their melt-mixed polypropylene-based nanocomposites has been observed by Menzer et al [30]
Compared to Nanocyl NC7000 and Baytubes C150P, MWCNT-VAST exhibited a (101) peak at 44.1°, which originates from a lateral correlation between graphite layers [56]
Summary
The multi-walled carbon nanotube (MWCNT) with the largest aspect ratio resulted in composites with the best X-band microwave absorption performance, which is considerably better than that of reported pristine CNT/polymer composites with similar or lower thicknesses and CNT loadings below 4 wt%
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