Effect of functionalization of carbon nanotubes on the radar-absorbing properties of polymeric composites based on them

Abstract

The effect of functionalization of carbon nanotubes in a mixture of sulfuric and nitric acids on the radar-absorbing properties of polymeric composites based on them was studied. The optimum functionalization conditions were determined, allowing the thickness of the radar-absorbent material to be decreased by 36-46% (with its characteristics preserved) relative to the analogous composites with unmodifi ed nanotubes.Radar-adsorbent materials (RAMs) are used for the absorption of the incident electromagnetic radiation (EMR) at minimal refl ection level, which allows solution of diverse problems, from the absorption of "parasitic" radiations inside high-frequency units of various devices to a decrease in the radiolocation visibility of military items. Polymeric composites with carbon nanotubes (CNTs) as RAMs have been extensively studied recently. Various procedures are used for CNT modifi cation aimed at increasing the effi ciency of EMR absorption. They are mostly based on incorporation of various substances (metals [1-4], alloys [5], oxides [6,7], salts [8]), on the surface and/or into internal voids of CNTs. Depending on the concentration of the modifying substances, they occur in the forms of a surface layer, of nanothreads inside the CNTs, or of particles inside CNTs or on their surface. Such procedures are aimed at altering the electrophysical properties of the CNTs themselves. On the other hand, the properties of the composites under consideration are strongly infl uenced not only by the parameters of the nanotubes, but also by the character of their distribution in the polymeric matrix. It is known that the initial CNTs are distributed in the polymeric matrix nonuniformly because of their tendency to agglomeration. The same is true for the nanotubes modifi ed by the above procedures. The widely used way to reach uniform distribution in the polymeric matrix is chemical modifi cation (functionalization) of CNTs with the formation of active functional groups (e.g., carboxy groups) on their surface. However, the effect of CNT functionalization on the radar-absorbing properties of polymeric composites based on them was not studied in detail previously.In this work we studied the radar-absorbing properties of polymeric composites with CNTs in relation to the CNT content and degree of functionalization.The radar-absorbing properties were studied in the range 52-73 GHz (millimeter wavelength range). The devices operating in this range include those for measuring the fl ow rate, humidity, and compressibility coeffi cient of gases, airplane landing systems, protected communication systems, devices for studying rapid processes, some medical devices, systems for detection and high-precision following of low-fl ying and mobile surface targets, and antenna feeder systems for on-board radioelectronic systems. EXPERIMENTALOur experiments were performed with CNTs of grade Taunit-M [TU (Technical Specifi cation) 2166-

Effect of the Morphology and Structure on the Microwave Absorbing Properties of Multiwalled Carbon Nanotube Filled Epoxy Resin Nanocomposites

“…The loss mechanisms may be physical, chemical or both simultaneously. Nowadays, researches involving RAM cover the frequency range from 1 to 100 GHz 3,4,5 .…”

The influence of functionalization time of carbon nanotube on the mechanical properties of the epoxy composites

“…Earlier we have investigated that the length of CNT was depended on their functionalization time. 21 It was determined that length of f-CNT medium is 1.25, 0.62, 0.36, and 0.25 µm at 0.5, 2, 7, and 15 h of functionalization time, respectively. The mean length of each type of f-CNT can be determined by different statistical methods.…”

Structure Design, Surface Modification, and Application of CNT Microwave‐Absorbing Composites

“…Zakharychev et al. [ 168 ] investigated the effect of functionalization of CNTs in the mixture of sulfuric acid and nitric acid on the microwave absorption properties of CNTs. The main factors affecting the microwave absorption properties are the length of CNTs, which determines the conductivity and permeability threshold of the composite, as well as the presence of functional groups, which facilitate the uniform distribution of CNTs in the polymer.…”