title: The impact of different multi-walled carbon nanotubes on the X-band microwave absorption of their epoxy nanocomposites.
abstract: BACKGROUND
  Carbon 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.
  
  
  RESULTS
  The 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%.
  
  
  CONCLUSIONS
  A 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 AbstractComparison of the X-band microwave reflection loss of epoxy composites of various commercial multi-walled carbon nanotube materials.
authors.affiliation: National Key Laboratory of Polymer and Composite Materials, Ho Chi Minh City University of Technology (HCMUT), Vietnam National University, 268 Ly Thuong Kiet, District 10, Ho Chi Minh City, Vietnam.
authors.forename: Bien Dong
authors.initials: BD
authors.lastname: Che
authors.affiliation: National Key Laboratory of Polymer and Composite Materials, Ho Chi Minh City University of Technology (HCMUT), Vietnam National University, 268 Ly Thuong Kiet, District 10, Ho Chi Minh City, Vietnam.
authors.forename: Bao Quoc
authors.initials: BQ
authors.lastname: Nguyen
authors.affiliation: Faculty of Materials Technology, Ho Chi Minh City University of Technology, Vietnam National University, 268 Ly Thuong Kiet, District 10, Ho Chi Minh City, Vietnam.
authors.forename: Le-Thu T
authors.initials: LT
authors.lastname: Nguyen
authors.affiliation: Faculty of Materials Technology, Ho Chi Minh City University of Technology, Vietnam National University, 268 Ly Thuong Kiet, District 10, Ho Chi Minh City, Vietnam ; Materials Technology Key Laboratory (Mtlab), Ho Chi Minh City University of Technology, Vietnam National University, 268 Ly Thuong Kiet, District 10, Ho Chi Minh City, Vietnam.
authors.forename: Ha Tran
authors.initials: HT
authors.lastname: Nguyen
authors.affiliation: National Key Laboratory of Polymer and Composite Materials, Ho Chi Minh City University of Technology (HCMUT), Vietnam National University, 268 Ly Thuong Kiet, District 10, Ho Chi Minh City, Vietnam.
authors.forename: Viet Quoc
authors.initials: VQ
authors.lastname: Nguyen
authors.affiliation: Faculty of Materials Technology, Ho Chi Minh City University of Technology, Vietnam National University, 268 Ly Thuong Kiet, District 10, Ho Chi Minh City, Vietnam ; Materials Technology Key Laboratory (Mtlab), Ho Chi Minh City University of Technology, Vietnam National University, 268 Ly Thuong Kiet, District 10, Ho Chi Minh City, Vietnam.
authors.forename: Thang
authors.initials: T
authors.lastname: Van Le
authors.affiliation: National Key Laboratory of Polymer and Composite Materials, Ho Chi Minh City University of Technology (HCMUT), Vietnam National University, 268 Ly Thuong Kiet, District 10, Ho Chi Minh City, Vietnam.
authors.forename: Nieu Huu
authors.initials: NH
authors.lastname: Nguyen
keywords: Carbon nanotubes; Epoxy composites; Nanocomposites; Radar absorbing materials (RAMs); X-band microwave absorption